Cassava new variety of anti-mite identification and new type of high-density planting control cultivation method

Abstract

The application discloses a cassava new variety mite resistance identification and a new type of high-density planting and pest control cultivation method. The mite resistance identification adopts "indoor preliminary screening-field verification-comprehensive determination": taking 'C1115' and 'SC205' as references, the development period, egg production, hatching rate and adult life of leaf mites are determined, and a comprehensive relative resistance coefficient is calculated to determine the grade; in the field, the relative mite damage index is taken as the core, and multi-year repeated investigation is combined to comprehensively evaluate. The method overcomes the defects of single index determination, fixed threshold value, and inapplicability of cross-year and cross-ecological zone, shortens the early screening period by more than 90%, and balances the identification efficiency and the result reliability. Based on the identification result, the mite-resistant varieties are selected for single ridge equilateral triangle high-density planting, and are matched with stem treatment, precise fertilization, insect condition monitoring and biological pesticide prevention and control. Compared with traditional cultivation, the mite damage index of the mode is reduced by 50.4%, and the yield is increased by 21.3%, so that the green prevention and control and yield increase are coordinated, and technical support is provided for cassava mite-resistant breeding and popularization.

Description

Technical Field

[0001] This invention relates to the field of cassava technology, specifically to the identification of the mite resistance of a new cassava variety and a novel dense planting method for pest control. Background Technology

[0002] Cassava ( Manihot esculenta It is a typical tropical crop and a staple food for more than 1 billion people worldwide, and it is also an important specialty food and cash crop in my country.

[0003] Cinnabar spider mite ( Tetranychus cinnabarinus Two-spotted spider mite ( Tetranychus urticae Belonging to the Tetranychidae family of the Acari subclass, it is a global agricultural pest that is prevalent in cassava production. It has an extremely wide host range and can harm more than 1,100 plant species, including cassava. It mainly gathers on the back of cassava leaves to suck sap, causing the affected leaves to fade and turn yellow. In severe cases, it can cause premature aging of the plant or even the death of the entire plant, significantly reducing the yield of cassava tubers and the quality of starch. It has become a dominant pest of cassava.

[0004] Currently, the control of spider mites in cassava production mainly relies on chemical spraying. However, because my country's main cassava producing areas are mostly located in arid and semi-arid regions lacking stable water sources, coupled with the short life cycle, high reproductive rate, strong adaptability, and easy development of pesticide resistance in spider mites, chemical control is not only difficult to implement, but long-term and excessive use has also led to increasingly prominent pesticide resistance problems. Excessive and frequent inappropriate use of pesticides has also brought about a series of problems such as pesticide residues in agricultural products, damage to the ecological environment of production areas, and non-target biological toxicity, seriously restricting the green and sustainable development of the cassava industry. Therefore, finding effective measures to control cassava spider mites at the source has become a major problem that urgently needs to be solved in the current development of the cassava industry. Breeding and utilizing mite-resistant varieties is an economical, simple, and effective way to achieve green control of spider mites at the source. However, different cassava varieties exhibit significant differences in their resistance mechanisms and resistance capabilities to spider mites, necessitating the establishment of scientific and standardized methods for identifying mite resistance to provide technical support for the screening and promotion of mite-resistant varieties. Currently, the main basis for identifying the insect resistance of cassava germplasm resources is the industry standard NY / T 2445-2013, "Technical Regulations for Identifying Insect Resistance of Cassava Germplasm Resources." This standard specifies the technical methods and evaluation criteria for indoor and field resistance identification of cassava germplasm resources against the spider mite *Tetranychus carmineus* and the cassava mite *Tetranychus cassavaus*. However, this standard still has the following shortcomings in practical application: First, indoor identification relies on a single indicator (F1 generation survival rate) as the basis for judgment, while the adverse effects of mites on resistant hosts are multi-dimensional. In addition to decreased survival rate, it also manifests as a comprehensive deterioration of life parameters such as prolonged developmental period, reduced egg production, decreased hatching rate, and shortened adult lifespan. A single survival rate indicator cannot comprehensively and accurately reflect the overall resistance level of cassava varieties to spider mites. Second, there is a lack of organic integration between indoor and field identification methods. This standard treats indoor identification (based on F1 generation survival rate) and field identification (based on mite infestation index) as two independent methods, failing to establish a progressive identification process from rapid indoor screening to field verification and confirmation, and also lacking a corresponding conversion relationship between indoor indicators and field grades. Thirdly, it lacks a continuous quantitative grading system based on dual reference varieties of highly resistant and highly susceptible varieties. Although the standard sets up 'South China 205' (susceptible control) and 'C1115' (resistant control), it uses a fixed mite infestation index range for grading (e.g., mite infestation index 0.1~12.5 for highly resistant, 12.6~37.5 for resistant). This fixed threshold lacks comparability across different ecological zones and years due to environmental differences, and it has not yet established relative evaluation indicators (such as relative resistance coefficients or relative mite infestation indexes) anchored by the measured mean of the dual reference varieties, making it difficult to compare identification results across regions and batches.

[0005] Currently, various new cassava varieties with excellent comprehensive traits are constantly emerging. Among them are varieties with upright plant type, outstanding yield, high starch content and low hydrocyanic acid content, which have both fresh consumption and processing value and huge potential for promotion. However, the resistance ability and resistance mechanism of most new varieties to spider mites are not yet clear, and there is a lack of suitable green control cultivation measures, which cannot provide technical support for their promotion and planting. Reasonable dense planting, as a classic cultivation regulation technique, can affect the feeding, reproduction and spread of pests by changing the field microenvironment and regulating the ventilation and light conditions between plants, thereby improving crop yield and quality. However, excessively high planting density can easily lead to closed field and poor ventilation and light, which can aggravate the occurrence of pests and diseases; while too low a density cannot give full play to the group pest control effect and will also reduce land utilization and total yield. Therefore, for cassava varieties with known mite resistance, determining the most suitable dense planting density is the key to achieving synergistic effects of "mite-resistant varieties + dense planting pest control". However, there are currently no systematic research reports on combining the identification of cassava variety mite resistance with supporting high-density planting techniques.

[0006] In summary, existing cassava mite resistance identification techniques suffer from several drawbacks, including the use of single indoor indicators, excessively long field cycles, a disconnect between indoor and outdoor methods, and a lack of a dual-reference quantitative grading system. Furthermore, there are no research reports combining mite resistance identification with supporting high-density planting techniques. There is an urgent need to establish a standardized method that integrates rapid indoor identification and field verification of cassava variety mite resistance, and to develop targeted high-density planting and pest control programs based on the identification results, providing technical support for the screening and promotion of mite-resistant cassava varieties. Summary of the Invention

[0007] To address the aforementioned technical problems, the purpose of this invention is to provide a method for identifying the mite resistance of new cassava varieties and a novel high-density planting method for pest control. This invention first establishes a standardized method for identifying mite resistance by combining rapid indoor identification with field verification, clarifying the mite resistance ability and resistance level of the cassava varieties to be tested. Based on this, for varieties with clearly defined mite resistance levels, the most suitable regional high-density planting parameters are determined, forming a synergistic green pest control technology model of "variety mite resistance identification—resistance level determination—high-density planting pest control," thereby achieving a synergistic effect of controlling cassava spider mites at the source and increasing yield.

[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solution: The first objective of this invention is to provide a method for identifying the mite resistance of a new cassava variety, comprising the following steps: S1, Indoor Identification (1) Preparation of test leaves: Place the middle mature leaves of the highly mite-susceptible reference variety, the highly mite-resistant reference variety, and the new cassava variety to be tested with the back facing up on a moist substrate; (2) F1 generation rearing and index determination: One-day-old female adult mites were inoculated on the back of the leaves. After 24 hours of inoculation, the eggs laid by the one-day-old female adult mites were collected and the one-day-old female adult mites were removed. The leaves were artificially reared, and the developmental period of the F1 generation hatched from the eggs on the leaves was recorded. The developmental period included the egg stage, larval stage, nymphal stage and adult stage. After the F1 generation developed into adults, the female adult mites of the F1 generation were paired with male adult mites. The number of eggs laid by a single female adult mite was recorded daily until death. The egg hatching rate and the lifespan of the F1 generation adults were calculated. There were at least 3 replicates for each species, and each replicate consisted of at least 10 leaves, that is, at least 30 independent female mites for each species. (3) Mite resistance determination: Calculate the arithmetic mean of the four indicators of developmental duration, single female egg production, egg hatching rate, and adult lifespan for the highly mite-resistant reference variety, the highly mite-susceptible reference variety, and the new cassava variety to be tested. Let R represent the arithmetic mean of the indicators for the highly mite-resistant reference variety, S represent the arithmetic mean of the indicators for the highly mite-susceptible reference variety, and T represent the arithmetic mean of the indicators for the new cassava variety to be tested. Based on the arithmetic mean of the four indicators for the highly mite-resistant reference variety, the highly mite-susceptible reference variety, and the new cassava variety to be tested, calculate the relative resistance coefficient RRC1 for single female egg production, the relative resistance coefficient RRC2 for egg hatching rate, and the relative resistance coefficient RRC3 for adult lifespan, and then calculate the comprehensive relative resistance coefficient RRC. avg According to the comprehensive relative resistance coefficient RRC avg The range of mite resistance of the tested cassava varieties is determined as high mite resistance, mite resistance, moderate mite resistance, mite susceptibility, or high mite susceptibility. The arithmetic mean of the average values ​​within all replicate groups is taken as the arithmetic mean of the four indicators: developmental duration, number of eggs laid by a single female, egg hatching rate, and adult lifespan. The relative resistance coefficients RRC1 (single female egg production), RRC2 (egg hatching rate), and RRC3 (adult lifespan) are calculated using the following formulas. RRC1=(S 单雌产卵量 -T 单雌产卵量 ) / (S 单雌产卵量 -R 单雌产卵量 )×100%; RRC2=(S 卵孵化率 -T 卵孵化率 ) / (S 卵孵化率 -R 卵孵化率 )×100%; RRC3=(S 成虫寿命 -T 成虫寿命 ) / (S 成虫寿命 -R 成虫寿命 )×100%; Among them, T 单雌产卵量 T卵孵化率 T 成虫寿命 S represents the arithmetic mean of single female egg production, the arithmetic mean of egg hatching rate, and the arithmetic mean of adult lifespan for the tested cassava variety. 单雌产卵量 S 卵孵化率 S 成虫寿命 R represents the arithmetic mean of the number of eggs laid per female, the arithmetic mean of the egg hatching rate, and the arithmetic mean of the adult lifespan of the highly susceptible mite reference species. 单雌产卵量 R 卵孵化率 R 成虫寿命 The arithmetic mean of single female oviposition, the arithmetic mean of egg hatching rate, and the arithmetic mean of adult lifespan are given for the high mite-resistant reference varieties. The relative resistance coefficient (RRC4) of the developmental stage index is calculated using the following formula: RRC4=(T 发育历期 -S 发育历期 ) / (R 发育历期 -S 发育历期 )×100%; Among them, T 发育历期 S is the arithmetic mean of the developmental duration of the new cassava variety to be tested. 发育历期 R is the arithmetic mean of the developmental period of a highly susceptible mite reference variety. 发育历期 This is the arithmetic mean of the developmental period of the high mite-resistant reference variety; The arithmetic mean of RRC1, RRC2, RRC3, and RRC4 is taken respectively, and the comprehensive relative resistance coefficient RRC of the tested cassava variety is calculated. avg ; RRC avg =(RRC1+RRC2+RRC3+RRC4) / 4 When the RRC avg A concentration of ≥80% is considered high mite resistance; 60% ≤ RRC avg If the RRC value is less than 80%, it is considered anti-mite; the value of 40% ≤ RRC is considered anti-mite. avg If the RRC is less than 60%, it is considered moderately mite-resistant; the above 20% ≤ RRC avg If <40%, it is determined to be mite-susceptible; if the aforementioned RRC avg If the percentage is less than 20%, it is considered highly susceptible to mites; S2, Field Identification (1) Select the seed tubers of the new cassava variety to be tested, the reference variety with high mite resistance, and the reference variety with high mite susceptibility for field planting. After emergence, conduct an insect survey every 30 days until the cassava is harvested in the same year. (2) During each pest survey, plants were randomly selected from the new cassava variety to be tested, the highly mite-resistant reference cassava variety, and the highly mite-susceptible reference cassava variety. For each plant, 12 fully expanded leaves were taken from the upper, middle, and lower parts. The damage level, the number of leaves with the damage level, and the total number of mites on each fully expanded leaf were counted. The mite damage index I and the relative mite damage index RDI of the new cassava variety to be tested, the highly mite-resistant reference cassava variety, and the highly mite-susceptible reference cassava variety were calculated to determine the field mite resistance level of the new cassava variety to be tested. The mite infestation index, expressed as a percentage, is calculated using the following formula: I = [∑(leaf damage level × number of leaves with damage level) / (total number of leaves surveyed × highest representative value)] × 100%; The highest level represents a value of 4; The Relative Mite Infestation Index (RDI), expressed as a percentage, is calculated using the following formula: RDI = (I T -I S ) / (I R -I S ) × 100%; Among them, I T I represents the mite infestation index of the tested variety. S As a reference variety for highly susceptible mites, I R The mite infestation index is used as a reference variety for high mite resistance. (3) Resistance determination: When RDI ≥ 80%, it is determined to be highly mite resistant; when 60% ≤ RDI < 80%, it is determined to be mite resistant; when 40% ≤ RDI < 60%, it is determined to be moderately mite resistant; when 20% ≤ RDI < 40%, it is determined to be susceptible to mites; when RDI < 20%, it is determined to be highly susceptible to mites. S3, Comprehensive Judgment When the indoor mite resistance level of the tested cassava variety is inconsistent with the field mite resistance level of the tested cassava variety, the field mite resistance level shall prevail; if reliable data cannot be obtained from field identification due to uncontrollable factors, the indoor mite resistance level of the tested cassava variety shall prevail. The highly mite-susceptible reference cassava variety is 'SC205', and the highly mite-resistant reference cassava variety is 'C1115'.

[0009] The beneficial effects of this invention are as follows: This invention clearly uses 'C1115' (resistant to mites) and 'SC205' (susceptible to mites) as representative reference varieties, and constructs an indoor evaluation index system based on four core life parameters: developmental duration, egg production per female, egg hatching rate, and adult lifespan. This comprehensively covers the three dimensions of growth and development, reproductive capacity, and survival ability of mites, overcoming the deficiency of existing standards that only use the F1 generation survival rate as a single judgment indicator. Simultaneously, it innovatively proposes the quantitative evaluation index of "Comprehensive Relative Resistance Coefficient (RRC_avg)," positioning the mean value of the tested varieties at a relative position between the two endpoints of high resistance and high susceptibility. This overcomes the deficiency of the lack of comparability of fixed mite pest index thresholds in different years and ecological ranges, and the identification results... Objective and repeatable, this invention organically combines rapid indoor screening (S1) with field verification (S2), and clearly defines a comprehensive judgment rule of "field priority, indoor supplementation," forming a progressive dual-track identification process of "indoor screening → field verification → comprehensive judgment." This ensures both identification efficiency and result reliability, overcoming the technical problem of disconnect between indoor and outdoor methods in existing technologies. Most importantly, this invention's indoor identification can complete the initial resistance assessment in only 15-25 days, compared to the traditional field identification method which takes more than 12 months. This shortens the early screening cycle of resistant germplasm by more than 90%, allowing breeders to eliminate mite-susceptible materials and focus on superior mite-resistant lines early in variety selection, significantly reducing the breeding time for mite-resistant cassava varieties. This invention's method is applicable to all types of new cassava varieties (lines), without being limited by variety type or planting area, providing standardized technical support for the screening, identification, and promotion of mite-resistant cassava varieties.

[0010] Furthermore, the relative resistance coefficient represents the relative position of the arithmetic mean of the indicators of the tested cassava variety between the highly mite-resistant reference variety and the highly mite-susceptible reference variety: When RRC is close to 0%, it indicates that the performance of the tested variety is close to that of the highly susceptible mite reference variety; when RRC is close to 100%, it indicates that the performance of the tested variety is close to that of the highly resistant mite reference variety; when RRC is between 0% and 100%, it indicates that the resistance level of the tested variety is between highly susceptible and highly resistant.

[0011] Furthermore, in step S2(1), the field planting is specifically carried out in accordance with NY / T 2445-2013 "Technical Regulations for Identification of Insect Resistance of Cassava Germplasm Resources".

[0012] Furthermore, the moisturizing matrix is ​​a sponge.

[0013] Furthermore, the inoculation amount in step S1 (1) is 100 mites / leaf; the 1-day-old female adult mite is a 1-day-old female adult mite of uniform size and development that has developed from the nymph.

[0014] Furthermore, in step S2(1), the field identification is repeated in different years, with a minimum of 3 repetitions.

[0015] The beneficial effects of adopting the above-mentioned further scheme are as follows: This invention uses a sponge as a moisturizing substrate, which has strong adsorption and long-lasting water retention, and can keep cassava leaves fresh throughout the identification period, providing a stable feeding environment for the tested spider mites; the inoculation amount is limited to 100 mites / leaf, and one-day-old female adult mites developed from nymphs of uniform size and development are used as inoculation materials, which effectively eliminates the influence of differences in insect bodies on the experimental results, ensures the consistency of insect sources among treatments and the reliability of experimental results; field insect surveys are repeated at least three times in different years, which effectively avoids the random errors caused by uncontrollable factors such as climate fluctuations in a single year, ensures the stability and accuracy of field mite resistance identification results, and provides reliable data support for the systematic evaluation of the mite resistance ability of new cassava varieties.

[0016] Furthermore, the grading criteria for the damage level described in step S2 (2) are as follows: Level 0, no damage symptoms; Level 1, yellowish-white spots occupying <25% of the leaf area; Level 2, yellowish-brown / rust-red spots occupying 26%~50% of the leaf area; Level 3, yellowish-brown / rust-red spots occupying 51%~75% of the leaf area, or leaves curling; Level 4, yellowish-brown / rust-red spots occupying ≥76% of the leaf area, leaves scorched and falling off.

[0017] The beneficial effects of adopting the above-mentioned further scheme are as follows: This invention directly references the damage grading standards (0-4 levels) for *Tetranychus cinnabarinus* and *Monoclawus cassavaus* in NY / T 2445-2013, ensuring that the grading method is consistent with the current industry standards and has good compatibility and operability; this grading standard, together with the mite damage index calculation formula and relative mite damage index judgment rules in this invention, forms a complete field evaluation chain, realizing the transformation of resistance level from qualitative description to quantitative judgment, which greatly facilitates breeders and agricultural technicians to quickly and accurately classify and compare the resistance of different cassava varieties, and provides a direct basis for formulating differentiated field mite management strategies.

[0018] Furthermore, the number of eggs collected in step S1 should ensure that at least 10 test mites are observed for each species and each stage of the mites (egg stage, larval stage, nymphal stage, and adult stage).

[0019] Furthermore, the female and male adult mites of the F1 generation described in S1 are paired in a 1:1 ratio.

[0020] Furthermore, the culture conditions of the artificial climate chamber in step S1 (1) are: temperature 28±1℃, relative humidity 75%±5%, and photoperiod 14 (L): 10 (D).

[0021] The beneficial effects of adopting the above-mentioned further scheme are as follows: By setting up standardized artificial climate chamber culture conditions, this invention ensures that the test insects in each treatment group are in a consistent temperature, humidity, and light environment, eliminating the interference of environmental factors on the growth and development of spider mites, and ensuring the comparability of index measurements and the reliability of experimental results among different varieties; by ensuring that at least 10 test insects are observed for each variety and each developmental stage, the statistical requirements for sample size at each developmental stage are guaranteed, making the measured developmental history data statistically significant; at the same time, pairing F1 generation female and male adult mites at a 1:1 ratio simulates the sex ratio structure under natural conditions, making the measurement of reproductive parameters such as egg production, hatching rate, and adult lifespan closer to real biological laws, and improving the accuracy of identification results. This invention not only enables the grading and determination of the mite resistance of various new cassava varieties, but also comprehensively analyzes the inhibitory effect of new cassava varieties on the growth, development and reproduction of spider mites by systematically measuring four core life parameters: developmental period, single female egg production, egg hatching rate and adult lifespan. This provides detailed biological data support for a deeper understanding of the mite resistance mechanism of cassava varieties and provides an important theoretical basis for the precise utilization of mite-resistant varieties and the optimization of supporting pest control cultivation models.

[0022] The second objective of this invention is to provide a novel high-density pest control cultivation method for cassava, wherein a new cassava variety identified using the aforementioned mite resistance identification method is planted. The specific steps are as follows: (1) Seed stem treatment: Select healthy, disease-free, undamaged, and plump buds from the seed stem segments of the new cassava variety selected by the aforementioned mite resistance identification method, and disinfect and dry the cut ends of the seed stem segments; (2) Site selection and land preparation and fertilization: Select a flat and well-drained site, deep plow the site and level it, then apply base fertilizer and plow and mix it evenly. (3) Dense planting: When the temperature is stable above 15℃ and the soil 0-20cm layer is moist after rainfall, the seedlings are planted in a single-ridge equilateral triangle dense planting pattern; the seedlings are inserted obliquely into the soil, the soil is compacted, and the seedlings are managed according to the conventional field management plan. (4) Insect monitoring and scientific application of pesticides: After the cassava seedlings emerge, insect monitoring should be carried out every 10 to 15 days; when the average insect population density per single leaf exceeds 10 or the rate of damaged plants reaches 10%, biological agents should be sprayed for control. (5) Harvesting: 8 to 10 months after planting, when the lower leaves of the cassava plant begin to turn yellow and fall off, and the tubers stop expanding, the cassava can be harvested.

[0023] The beneficial effects of this invention are as follows: This invention constructs a collaborative prevention and control technology model of "precise identification of mite resistance in new cassava varieties—mite resistance in the variety itself—adapted dense planting for pest control—supporting green management." By optimizing the field population structure and ventilation and light conditions through equilateral triangular dense planting on single ridges, it further strengthens the field microenvironment unfavorable to the breeding and spread of spider mites on the basis of the variety's own resistance, achieving synergistic effects of source control of mite-resistant varieties and regulation of the dense planting environment. Throughout the process, biological agents such as abamectin, matrine, or azadirachtin are given priority for pest control, avoiding the resistance and environmental pollution problems caused by chemical acaricides, reducing the amount of pesticides and fertilizers used, and effectively reducing production costs and ecological environmental pressure. At the same time, this dense planting model is highly versatile and can be applied across regions, which can give full play to the high-yield potential of various mite-resistant new cassava varieties, improve cassava yield and quality, and thus increase the economic benefits of growers, providing strong technical support for the large-scale promotion of new cassava varieties and the green and sustainable development of the industry.

[0024] Furthermore, the length of the seed stem segment mentioned in step (1) is 15 cm to 20 cm, and 2 to 3 buds are retained; The disinfection method described in step (1) is to dip the cut end of the seed stem segment in wood ash, or soak it in a 1000-fold dilution of 50% carbendazim wettable powder for 3-5 minutes, and then let it dry before use.

[0025] Furthermore, the deep tillage depth mentioned in step (2) is 25 cm to 30 cm; The plots mentioned in step (2) should avoid being selected from plots where crops that are prone to spider mite infestation were previously planted; The base fertilizer mentioned in step (2) includes bio-organic fertilizer, phosphate fertilizer, and compound fertilizer, and the amount of base fertilizer used is per 667 m³. 2 Apply 500 kg to 800 kg of the bio-organic fertilizer, 50 kg of the phosphate fertilizer, and 30 kg to 40 kg of the compound fertilizer; The mass ratio of N, P2O5, and K2O in the compound fertilizer is 15:15:15.

[0026] Furthermore, the plots mentioned in step (2) should avoid being selected from plots where crops such as melons and corn, which are prone to spider mites, were previously planted.

[0027] Furthermore, in step (3), the single-ridge equilateral triangle dense planting pattern has a plant spacing of 60 cm; When planting the seed stem segment, the insertion depth is 1 / 2 to 2 / 3 of the length of the seed stem segment, with the bud facing upwards; The specific field management is as follows: before the cassava rows close, manual weeding is carried out according to the growth of weeds; 30 to 40 days after transplanting, when the seedlings of the new mite-resistant cassava variety grow to 20 cm to 30 cm, topdressing fertilizer is applied once in combination with weeding and cultivation; during the tuber enlargement period 90 to 120 days after transplanting, tuber enlargement fertilizer is applied once.

[0028] The beneficial effects of adopting the above-mentioned further scheme are: it standardizes the planting materials and transplanting operations for cassava resistance identification tests, ensuring the uniformity and reliability of the experimental basis.

[0029] Furthermore, the topdressing of seedling fertilizer mentioned in step (3) specifically refers to applying fertilizer per 667 m³. 2 Apply 5-7 kg of urea and 10-15 kg of compound fertilizer as top dressing; the specific amount of top dressing for promoting growth is per 667 m². 2 Apply 10-15 kg of compound fertilizer and 10-15 kg of potassium fertilizer as top dressing; The mass ratio of N, P2O5, and K2O in the compound fertilizer is 15:15:15.

[0030] Further, the biological agent mentioned in step (4) is 1.8% abamectin emulsifiable concentrate at 5000 times dilution, 0.3% azadirachtin emulsifiable concentrate at 500~800 times dilution, or 1% matrine soluble concentrate at 500~800 times dilution; The spraying time mentioned in step (4) is on cloudy days and / or in the evening, and spraying is done once every 7 to 10 days, for a total of 2 sprayings.

[0031] The beneficial effects of adopting the above-mentioned further solutions are as follows: Based on the source control of mite-resistant varieties and the regulation of dense planting environment, this invention further optimizes the details of cultivation management; by selecting plots that avoid previous crops such as melons and corn, the initial source population of spider mites is reduced from the source; the base fertilizer is mainly bio-organic fertilizer supplemented by chemical fertilizer, combined with two precise topdressings during the seedling stage and the tuber enlargement stage, which promotes seedling growth and tuber development while avoiding excessive nitrogen fertilizer application that leads to excessive plant growth and spider mite proliferation; the preferred pesticides are bio-based agricultural agents such as abamectin, azadirachtin, or matrine. The pesticides are applied on cloudy days or in the evening to reduce the decomposition of strong light and improve the utilization efficiency of the pesticides. The amount of pesticides and fertilizers used is reduced by 30% to 40% compared with traditional cultivation, which effectively reduces the risk of pollution to the production area. At the same time, through the synergistic effect of reasonable dense planting and precise water and fertilizer management, the average mite infestation index is significantly reduced by 50.4% compared with traditional cultivation, and the fresh potato yield is increased by 21.3%. This achieves the synergistic goal of green control of spider mites and high-yield cultivation, and forms a three-in-one green control and high-yield cultivation technology system for cassava spider mites, which integrates "mite-resistant varieties - dense planting control - green management".

[0032] Furthermore, throughout the entire growth period in step (3), avoid waterlogging in the field, drain water promptly after rain, and prevent diseases such as root rot caused by excessive soil moisture.

[0033] Furthermore, as described in step (5), timely removal of crop residues and fallen leaves from the field after harvest, followed by deep burial or burning, can reduce the overwintering source of spider mites and lay the foundation for the next season's cultivation. Attached Figure Description

[0034] Figure 1 This refers to the developmental stages of the F1 generation of the two-spotted spider mite in Example 1 of the present invention; Figure 2 The figures represent the number of eggs laid by a single female and the hatching rate of the eggs in Embodiment 1 of the present invention; wherein (A) is the number of eggs laid by a single female; and (B) is the hatching rate of the eggs. Figure 3 This refers to the adult lifespan in Example 1 of the present invention; Figure 4 The two-spotted spider mite infestation index and its distribution range under different planting modes of 'GS1505' in Embodiment 3 of the present invention; wherein (A) is the mite infestation index under different planting modes of 'GS1505'; and (B) is the distribution range of the mite infestation index under different planting modes of 'GS1505'. Figure 5 The yield of 'GS1505' under different planting modes in Embodiment 3 of the present invention; Figure 6 The two-spotted spider mite infestation index and its distribution range under the DDM-4 and DS planting modes of 'GS1505' in Example 4 of the present invention; wherein (A) is the mite infestation index of DDM-4 and DS; and (B) is the distribution range of the mite infestation index of DDM-4 and DS. Figure 7 The yield of 'GS1505' under DDM-4 and DS planting modes in Example 4 of this invention; Figure 8 This is a field photo of 'GS1505' in this invention. Detailed Implementation

[0035] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0036] The test varieties and insect sources of this invention are shown below: The highly susceptible cassava variety 'SC205' was selected as the reference, and the highly resistant cassava variety 'C1115' was selected as the reference. The susceptible and resistant references were respectively tested for resistance to the two-spotted spider mite. T.urticaeThe cassava varieties exhibiting high susceptibility and high resistance (Liang, et al. 2022) all originated from the National Cassava Germplasm Resource Center. "Guishu 1505" (GS1505) is a new edible cassava variety bred by the Guangxi South Subtropical Agricultural Research Institute. The two-spotted spider mite was an experimental population reared indoors with cowpeas.

[0037] In the embodiments of the present invention, cassava varieties 'C1115' and 'SC205' were used as representative mite-resistant and mite-susceptible reference varieties, respectively. The indoor and field mite resistance of 'GS1505' was evaluated, as detailed below: Example 1: Indoor mite resistance assessment Fully mature leaves from the middle section of plants of 'SC205' (susceptible to mites), 'C1115' (resistant to mites), and the new cassava variety 'GS1505' were placed on completely moistened sponges in white porcelain dishes, with the undersides of the leaves facing upwards. The edges of the leaves were wrapped with moist absorbent paper to prevent subsequent insect escape. One-day-old two-spotted spider mites, developed from post-nymphs and of uniform size and development, were sampled at a rate of 100 mites per leaf. T.urticae Female adult mites were inoculated onto the underside of leaves. After 24 hours, the eggs laid by the female adult mites were collected, and the female adult mites on the underside of the leaves were removed to ensure that 10 test mites of each variety at each instar could be observed. White porcelain dishes were placed in an artificial climate chamber (temperature 28±1℃, relative humidity 75%±5%, photoperiod 14 L:10 D) for rearing.

[0038] The developmental stages (egg stage, larval stage, nymphal stage, and adult stage) of the F1 generation spider mites were observed and recorded every 0.5 days. After the F1 generation developed into adults, female and male adults were paired at a 1:1 ratio, and the number of eggs laid by a single female was observed and recorded daily until the female adults died. The eggs laid each day were collected, and the hatching rate and lifespan of the F1 generation adults were calculated. Each leaf of each variety was counted as one replicate, with at least 3 replicates per variety and 30 replicates per variety, meaning each replicate consisted of at least 10 leaves, or at least 30 independent female mites per variety.

[0039] The criteria and calculation formula for indoor mite resistance are as follows: (1) Indoor mite resistance identification standard: If the RRC avg If the percentage is ≥80%, it is considered to have high mite resistance; if it is 60% ≤ RRC, it is considered to have high mite resistance. avg If the RRC value is less than 80%, it is considered anti-mite; the value of 40% ≤ RRC is considered anti-mite. avg If the resistance is less than 60%, it is considered moderately mite-resistant; the requirement of 20% ≤ RRC is also considered. avg If <40%, it is determined to be mite-susceptible; if the aforementioned RRC avg If the percentage is less than 20%, it is considered highly susceptible to mites.

[0040] (2) Formula for calculating the relative resistance coefficient (RRC): Calculate the arithmetic mean of the four indicators for the highly mite-resistant reference variety (denoted as R), the highly mite-susceptible reference variety (denoted as S), and the new cassava variety to be tested (denoted as T) in terms of developmental duration, number of eggs laid per female, egg hatching rate, and adult lifespan.

[0041] A: Egg production per female, egg hatching rate, and adult lifespan. The lower the values ​​of these three indicators, the stronger the resistance of the cassava variety to spider mites. The relative resistance coefficients RRC1 (egg production per female), RRC2 (egg hatching rate), and RRC3 (adult lifespan) are calculated using the following formulas: Calculate according to the following formula; RRC1=(S 单雌产卵量 -T 单雌产卵量 ) / (S 单雌产卵量 -R 单雌产卵量 )×100%; RRC2=(S 卵孵化率 -T 卵孵化率 ) / (S 卵孵化率 -R 卵孵化率 )×100%; RRC3=(S 成虫寿命 -T 成虫寿命 ) / (S 成虫寿命 -R 成虫寿命 )×100%; Among them, T 单雌产卵量 T 卵孵化率 T 成虫寿命 S represents the arithmetic mean of single female egg production, the arithmetic mean of egg hatching rate, and the arithmetic mean of adult lifespan for the tested cassava variety. 单雌产卵量 S 卵孵化率 S 成虫寿命 R represents the arithmetic mean of the number of eggs laid per female, the arithmetic mean of the egg hatching rate, and the arithmetic mean of the adult lifespan of the highly susceptible mite reference species. 单雌产卵量 R 卵孵化率 R 成虫寿命 The arithmetic mean of single female oviposition, the arithmetic mean of egg hatching rate, and the arithmetic mean of adult lifespan are given for the high mite-resistant reference varieties. B: Developmental stage. The higher the value of this index, the stronger the resistance of the cassava variety to spider mites. Its relative resistance coefficient is calculated using the following formula: RRC4=(T 发育历期 -S 发育历期 ) / (R 发育历期 -S 发育历期 )×100%; Among them, T 发育历期 S is the arithmetic mean of the developmental duration of the new cassava variety to be tested. 发育历期 R is the arithmetic mean of the developmental period of a highly susceptible mite reference variety. 发育历期This is the arithmetic mean of the developmental period of the high mite-resistant reference variety; (3) Comprehensive Relative Resistance Coefficient (RRC) avg ) Calculation formula RRC avg =(RRC1+RRC2+RRC3+RRC4) / 4 The results are shown in Table 1. Figures 1 to 3 As shown in Table 1, the relative resistance coefficients of various indicators were calculated based on the highly susceptible variety 'SC205' and the highly resistant variety 'C1115', and the resistance level was determined according to the indoor determination rules. The calculation results are shown in Table 1.

[0042] Table 1. Results of indoor mite resistance identification of different cassava varieties against two-spotted spider mites. As shown in Table 1, the overall relative resistance coefficient (RRC) of 'GS1505' is 64.0%, indicating that its overall performance across the four life parameters falls between the highly susceptible 'SC205' and the highly resistant 'C1115', leaning more towards the highly resistant side (>60%). Among these, the highest RRC for single female oviposition (81.6%) is close to the highly resistant level, indicating that 'GS1505' has the most prominent inhibitory effect on spider mite reproduction; while the lowest RRC for adult lifespan (41.7%) indicates that 'GS1505' has a relatively weak effect on shortening the lifespan of adult spider mites. Overall, except for adult lifespan, the RRC values ​​for the other three indicators all exceed 60%, leading to a comprehensive assessment of mite resistance.

[0043] Example 2: Field mite resistance identification procedure (1) Selection and planting of seed tubers: Seed tubers of 'GS1505', 'C1115', and 'SC205' were selected according to the standard requirements of Zhang Rulian et al. (2006), and field production management was carried out according to the standard requirements of Huang Jie, Zhang Zhenwen, Yan Qingxiang, et al. 2009. Good Operating Practices (GAP) for Cassava Production: NY / T1681-2009; (2) According to the randomized block design, the three identification materials were planted in the identification nursery of Guangxi South Subtropical Agricultural Research Institute. Each variety was set up with 3 replicates, and 50 plants were planted in each replicate with a plant spacing of 80cm×100cm. The experiment was repeated for three consecutive years in 2021, 2022 and 2023. Field management was carried out in accordance with the usual procedures and no acaricides were applied.

[0044] (3) After the cassava seedlings emerge, pest surveys shall be conducted every 30 days until the cassava is harvested that year. During the survey, 10 plants per replicate shall be randomly selected, and 4 functional leaves from the upper, middle and lower parts of each plant shall be selected. The number of two-spotted spider mites on the leaves shall be counted. The specific procedures shall be carried out in accordance with NY / T 2445-2013 "Technical Regulations for Identification of Insect Resistance of Cassava Germplasm Resources" and the damage level shall be assessed according to the following 0-4 level standards: Grade 0: No symptoms of damage; Grade 1: Small yellow-white spots covering less than 25% of the leaf area; Grade 2: Yellow-brown / rust-red spots covering 26%~50% of the leaf area; Grade 3: Yellow-brown / rust-red spots covering 51%~75% of the leaf area, or leaves curling; Grade 4: Yellow-brown / rust-red spots covering ≥76% of the leaf area, leaves scorched and falling off.

[0045] The formula for calculating the mite infestation index is as follows: Mite Infestation Index (I, %) = [∑(Leaf damage level × Number of leaves at that damage level) / (Total number of leaves surveyed × Highest representative value)] × 100% The highest level represents a value of 4; The formula for calculating the Relative Mite Infestation Index (RDI) is as follows: Relative Mite Infestation Index (RDI, %) = (I T -I S ) / (I R -I S ) × 100% Among them, I T I represents the mite infestation index of the tested variety. S As a reference variety for highly susceptible mites, I R The mite infestation index serves as a reference variety for high mite resistance.

[0046] Evaluation criteria: If RDI ≥ 80%, it is considered highly mite-resistant; if 60% ≤ RDI < 80%, it is considered mite-resistant; if 40% ≤ RDI < 60%, it is considered moderately mite-resistant; if 20% ≤ RDI < 40%, it is considered susceptible to mites; if RDI < 20%, it is considered highly susceptible to mites. A comprehensive assessment is required. When the indoor mite resistance level of the tested cassava variety is inconsistent with the field mite resistance level of the tested cassava variety, the field mite resistance level shall prevail; if reliable data cannot be obtained from field identification due to uncontrollable factors, the indoor mite resistance level of the tested cassava variety shall prevail. The results of the three-year evaluation are shown in Table 2.

[0047] Table 2. Results of field survey on the resistance of different cassava varieties to two-spotted spider mite from 2021 to 2023. Table 2 shows that the average mite infestation index of the new cassava variety 'GS1505' is 34.35%, and the relative mite infestation index is 71.0%. According to the field mite resistance grading standard, its resistance level is resistant.

[0048] In summary, the field identification results are consistent with the indoor identification conclusions: the relative mite infestation index of 'GS1505' is 71.0%, and the comprehensive relative resistance coefficient is 64.0%. Both indicators correspond to the mite resistance level. The indoor and field identification conclusions are completely consistent. Therefore, it is finally confirmed that 'GS1505' has a resistance level of 'resistance' to the two-spotted spider mite.

[0049] Example 3: Screening of regionally suitable high-density planting control models for spider mites in new cassava varieties (1) Experiment time and location: In 2024, the test of the new cassava variety 'GS1505' was carried out in Baodao New Village, Danzhou City, and was conducted at the same time as the field mite resistance identification of the new cassava variety 'GS1505' in Example 2.

[0050] (2) Using the traditional cassava single-ridge double-row planting pattern as a control (plant spacing 80 cm, row spacing 100 cm, denoted as DS); a total of 5 dense planting patterns were set up for testing, namely: ①Dense planting pattern with double rows on a single ridge (plant spacing 80 cm, row spacing 80 cm, denoted as DSM); ② Single-row dense planting pattern (plant spacing 60 m, row spacing 60 cm, denoted as DDM-1); ③ Single-row dense planting pattern (plant spacing 80 cm, row spacing 80 cm, denoted as DDM-2); ④ Single-ridge equilateral triangle dense planting pattern (plant spacing 80 cm, denoted as DDM-3); ⑤ Single-ridge equilateral triangle dense planting pattern (plant spacing 60 cm, denoted as DDM-4); Each mode has a processing cell area of ​​66.7 m². 2 Each treatment was set up as a replicate, with three replicates for each treatment; the control and the five tested modes were planted starting on March 10, 2024.

[0051] (3) Field management and investigation: The field planting and management requirements and field mite resistance identification methods for the five tested dense planting patterns are the same as those for the field mite resistance identification in Example 2. Yield measurement and analysis were conducted on December 20, 2024. The yield calculation method was as follows: yield (t / hm²) 2 = (Number of plants in the plot × Average fresh potato weight per plant (kg)) / Plot area (m²) 2 ) × 10, the result is as follows Figure 4 , Figure 5As shown. By comparing the average mite infestation index and average yield of different planting patterns (DS, DSM, DDM-1, DDM-2, DDM-3, and DDM-4), the pest control effect and yield potential of each pattern were comprehensively evaluated. A regionally suitable high-density planting pest control pattern with good pest control effect against two-spotted spider mites and adapted to new cassava varieties was selected. This pattern can be universally adapted to various new cassava varieties.

[0052] Depend on Figure 4 , Figure 5 We can obtain: (1) The control effects of the five 'GS1505' dense planting patterns on two-spotted spider mites showed significant differences, with DDM-4 and DDM-3 showing the best control effects. The average mite indices of DDM-4 and DDM-3 were 26.43% and 26.98%, respectively, both significantly lower than those of DDM-2, DDM-1, DSM, and DS (34.23%, 34.74%, 35.10%, and 35.24%, respectively). Moreover, there was no significant difference between DDM-4 and DDM-3, and no significant difference between the average mite indices of DDM-2, DDM-1, DSM, and DS. Based on the average mite indices, the control effects of the 'GS1505' dense planting patterns on two-spotted spider mites, from largest to smallest, were DDM-4, ​​DDM-3, DDM-2, DDM-1, DSM, and DS.

[0053] (2) Except for the first survey, where all the mite indices were below 2.0% and there was no significant difference, the mite indices of DDM-3 and DDM-4 in the other 9 surveys were below 62.5% (mite indices were 8.04%~62.42% and 7.00%~62.36%, respectively). Only 7 of the DDM-2, DDM-1, DSM and DS surveys had mite indices below 62.5% (mite indices were 10.82%~53.94%, 11.68%~53.17%, 11.81%~53.18%, and 12.09%~53.29%, respectively). Furthermore, DDM-2, DDM-1, DSM, and DS all had mite infestation indices above 62.5% twice, with indices of 64.95% and 66.23%, 65.27% and 66.53%, 65.57% and 66.56%, and 65.88% and 66.61%, respectively. Based on the average mite infestation index distribution range, the control effect of the 'GS1505' dense planting pattern on two-spotted spider mites, from largest to smallest, was DDM-4, ​​DDM-3, DDM-2, DDM-1, DSM, and DS.

[0054] (3) The yield measurement results show that the average yields of DDM-3 and DDM-4 are 50.73 t / hm. 2 and 51.03 t / hm 2 It is significantly higher than DDM-2's 45.10 t / hm. 244.46 t / hm of DDM-1 2 43.18 t / hm of DSM 2 DS 42.96 t / hm 2 Based on average yield, the pest control effect of the 'GS1505' dense planting model on two-spotted spider mites, from largest to smallest, is as follows: DDM-4, ​​DDM-3, DDM-2, DDM-1, DSM, and DS.

[0055] (4) Optimal dense planting pattern screening conclusion: By comparing the average mite infestation index and average yield of different planting patterns such as DS, DSM, DDM-1, DDM-2, DDM-3 and DDM-4, ​​the pest control effect and yield potential of each pattern were comprehensively evaluated. DDM-4 (single ridge equilateral triangle dense planting, plant spacing 60 cm) was determined to be the most suitable 'GS1505' dense planting pattern. It has the best pest control effect on two-spotted spider mites and the highest yield. This pattern can be widely adapted to various new cassava varieties.

[0056] Example 4: Verification of the regional suitability of a new cassava variety for controlling spider mites using a dense planting model. Experimental materials and models: The tested variety was the new cassava variety 'GS1505'; the traditional single-ridge double-row planting model of cassava was used as the control (plant spacing 80 cm, row spacing 100 cm, denoted as DS); the tested dense planting model was the single-ridge equilateral triangle dense planting model selected in Part III (plant spacing 60 cm, denoted as DDM-4), which can be universally adapted to various new cassava varieties.

[0057] (1) The experiment was carried out in Danzhou, Baisha and Yazhou in Hainan Province to verify regional adaptability; the area of ​​each replicate plot was 666.7 m², and three replicates were set for each treatment; the planting time for DS and DDM-4 models were April 20, 2024 in Danzhou, April 22, 2024 in Baisha, and April 25, 2024 in Yazhou District, Sanya City.

[0058] (2) Field management and measurement: The field planting and management requirements and field mite resistance identification methods for the two tested dense planting models, DS and DDM-4, ​​were the same as those for the field mite resistance identification in Example 2; yield measurement and analysis were carried out on December 20, 2024, and the yield calculation method was: yield (t / hm) 2 = (Number of plants in the plot × Average fresh potato weight per plant (kg)) / Plot area (m²) 2 )×10.

[0059] By comparing the average mite infestation index and average yield of the DDM-4 model with the DS control model, this study verifies the adaptability of the DDM-4 model in different regions and its control effect on two-spotted spider mites, clarifies the feasibility of promoting this model in multiple regions of Hainan, and verifies its versatility for various new cassava varieties, such as... Figure 6 , 7 As shown.

[0060] Depend on Figure 6 , Figure 7 We can obtain: (1) The field mite infestation index survey and analysis results in Danzhou, Baisha and Yazhou showed that DDM-4 of 'GS1505' could significantly reduce the mite infestation index of two-spotted spider mites, with average mite infestation indices of 26.48%, 26.89% and 27.76%, respectively, which were significantly lower than those of DS (35.84%, 35.97% and 36.44%). The average reduction in mite infestation index was 26.1%, 25.2% and 23.8%, respectively, with an average reduction of 25.0% ( Figure 6 A). Furthermore, there were no significant differences in the mite infestation index at the three test sites for DDM-4, ​​indicating that its anti-mite effect has cross-regional consistency and stability.

[0061] (2) In 10 surveys, the mite infestation index of DDM-4 in Danzhou, Baisha, and Yazhou ranged from 1.55% to 62.42%, with all 10 surveys below 62.5% (the upper limit of the intermediate resistance level); while the mite infestation index of DS ranged from 1.81% to 66.13%, with only 8 surveys below 62.5%, and the remaining 2 surveys reaching as high as 63.69% to 66.13%, exceeding the intermediate resistance level range. This indicates that DDM-4's control effect on two-spotted spider mites is not only significantly better than DS, but also stable throughout the annual growth period, maintaining above the intermediate resistance level at each survey time point, effectively avoiding the risk of the mite infestation index breaking out to the mite-susceptible level in stages, and its field mite resistance is reliable ( Figure 6 B).

[0062] (3) The yield measurement results show that the average yield of 'GS1505' DDM-4 in Danzhou, Baisha and Yazhou is 48.92 t / hm. 2 47.75 t / hm 2 and 49.81 t / hm 2 It is significantly higher than DS's 41.56 t / hm. 2 41.12 t / hm 2 and 42.12 t / hm 2 ( Figure 7 ).

[0063] (4) The field results in Danzhou, Baisha and Yazhou further verified that DDM-4 of 'GS1505' can significantly reduce the two-spotted spider mite infestation index. The average yield increase at the three test sites reached 17.4% (yield increase range of 16.1%~18.3%), significantly improving cassava yield. It has a good pest control effect on the two-spotted spider mite and can be widely promoted and applied in production.

[0064] Example 5: High-density planting and pest control cultivation of new cassava varieties (1) Treatment of seed stems: Select robust, disease-free, undamaged 'GS1505' seed stems with plump buds. Select them according to the standard requirements of Zhang Rulian, Li Kaimian, Xie Zhenyu, et al. 2006. Cassava seed stems: NY / T 356-2006. Cut seed stem segments with a length of 15-20cm. Each segment retains 2-3 buds. Dip the cut end of the seed stem segment in wood ash or carbendazim wettable powder for disinfection. Dry the cut end before use to ensure that the cut end heals and reduce rotting after planting. (2) Site selection and land preparation and fertilization: Select a flat site with good drainage. Avoid sites where the previous crop was melons, corn, or other crops that are prone to spider mites. Deep plow the site to a depth of 25 cm to 30 cm, remove weeds, plant debris and stones, level the land, and then apply base fertilizer. The base fertilizer should be mainly well-rotted organic fertilizer and supplemented with chemical fertilizer. The amount of base fertilizer should be per 667 m³. 2 Apply 500-800 kg of bio-organic fertilizer, 50 kg of phosphate fertilizer, and 30-40 kg of compound fertilizer (N:P2O5:K2O=15:15:15). Spread the fertilizer evenly and then till it to mix it thoroughly so that the fertilizer is fully integrated with the soil. (3) Dense planting: The single-ridge equilateral triangle dense planting pattern (DDM-4, ​​plant spacing 60 cm) selected and verified in Example 4 was used for planting. The planting time was March 25, 2025 in Longzhou County, Guangxi. When planting, the treated seed stem segments were inserted obliquely into the soil to a depth of 1 / 2-2 / 3 of the length of the seed stem segment, with the buds facing upwards. After planting, the soil was compacted to ensure uniform seedling emergence.

[0065] (4) Field management: ① Weeding: Before the cassava rows close, weed manually according to the growth of weeds; avoid weeds competing with cassava for nutrients, and at the same time reduce the host plants of spider mites. ② Water and fertilizer management: About 30 days after transplanting, when the cassava seedlings grow to 20 cm to 30 cm, apply seedling fertilizer once, that is, per 667 m 2 Apply 5-7 kg of urea and 10-15 kg of compound fertilizer as top dressing; during the tuber enlargement period (90-120 days after transplanting), apply a tuber enlargement fertilizer once, specifically per 667 m². 2 Apply 10-15 kg of compound fertilizer and 10-15 kg of potassium fertilizer as top dressing; the mass ratio of N, P2O5, and K2O in the compound fertilizer should be 15:15:15. Throughout the growing season, avoid waterlogging in the field and drain water promptly after rain. (5) Insect monitoring and scientific pesticide application: After the cassava seedlings emerge, insect monitoring should be carried out every 10 to 15 days; when the average insect population density per single leaf exceeds 10 or the rate of damaged plants reaches 10%, apply 1.8% abamectin EC at 5000 times dilution, 0.3% azadirachtin EC at 500 to 800 times dilution, or 1% matrine soluble solution at 500 to 800 times dilution; spraying time should be chosen on cloudy days or in the evening, spraying once every 7 to 10 days, and spraying twice consecutively.

[0066] (6) Harvesting: When the leaves of the cassava plant begin to turn yellow and fall off, and the tubers stop expanding, it can be harvested. When harvesting, manual or mechanical digging should be used to avoid damaging the tubers. After harvesting, the plant debris and fallen leaves in the field should be removed in time and buried deeply or burned to reduce the overwintering source of spider mites and lay the foundation for the next season's cultivation.

[0067] Field photos of 'GS1505' Figure 8 As shown.

[0068] Table 3. Effects of different planting patterns on the two-spotted spider mite infestation index of cassava. Table 4. Effects of different planting patterns on cassava yield As shown in Tables 3 and 4, after adopting the dense planting and pest control cultivation method of the present invention, the average mite infestation index throughout the entire growth period was 18.06%, which was significantly reduced by 50.4% compared with the traditional monoculture (36.44%); the fresh potato yield was 48.65 t / hm. 2 Compared to traditional monoculture (40.12 t / hm), 2 The new high-density planting method significantly increased yield by 21.3%. Especially during the peak two-spotted spider mite infestation period (July-September, tuber enlargement stage), the mite infestation index was only 10.40%–18.44%, while the traditional monoculture method reached 27.60%–37.19%, a reduction of 50%–62%. These results demonstrate that the new high-density planting method of this invention achieved significant pest control, effectively protecting cassava yield while significantly reducing the two-spotted spider mite infestation index and leaf damage, thus achieving the synergistic goal of green spider mite control and high-yield cultivation.

[0069] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for identifying the mite resistance of a new cassava variety, characterized in that, Includes the following steps: S1, Indoor Identification (1) Preparation of test leaves: Place the middle mature leaves of the highly mite-susceptible reference variety, the highly mite-resistant reference variety, and the new cassava variety to be tested with the back facing up on a moist substrate; (2) F1 generation rearing and index determination: One-day-old female adult mites were inoculated on the underside of the leaves. After 24 hours of inoculation, the eggs laid by the one-day-old female adult mites were collected and the one-day-old female adult mites were removed. The leaves were artificially reared, and the developmental period of the F1 generation hatched from the eggs on the leaves was recorded. The developmental period included the egg stage, larval stage, nymphal stage and adult stage. After the F1 generation developed into adults, the female adult mites of the F1 generation were paired with male adult mites. The number of eggs laid by a single female adult mite was recorded daily until death. The egg hatching rate and the lifespan of the F1 generation adults were calculated. There were at least 3 replicates for each species, and each replicate consisted of at least 10 leaves. (3) Mite resistance determination: Calculate the arithmetic mean of the four indicators of developmental duration, single female egg production, egg hatching rate, and adult lifespan for the highly mite-resistant reference variety, the highly mite-susceptible reference variety, and the new cassava variety to be tested. Let R represent the arithmetic mean of the indicators for the highly mite-resistant reference variety, S represent the arithmetic mean of the indicators for the highly mite-susceptible reference variety, and T represent the arithmetic mean of the indicators for the new cassava variety to be tested. Based on the arithmetic mean of the four indicators for the highly mite-resistant reference variety, the highly mite-susceptible reference variety, and the new cassava variety to be tested, calculate the relative resistance coefficient RRC1 for single female egg production, the relative resistance coefficient RRC2 for egg hatching rate, and the relative resistance coefficient RRC3 for adult lifespan, and then calculate the comprehensive relative resistance coefficient RRC. avg According to the comprehensive relative resistance coefficient RRC avg The range of mite resistance of the tested cassava varieties is determined as high mite resistance, mite resistance, moderate mite resistance, mite susceptibility, or high mite susceptibility. The arithmetic mean of the average values ​​within all replicate groups is taken as the arithmetic mean of the four indicators: developmental duration, number of eggs laid by a single female, egg hatching rate, and adult lifespan. The relative resistance coefficients RRC1 (single female egg production), RRC2 (egg hatching rate), and RRC3 (adult lifespan) are calculated using the following formulas. RRC1=(S 单雌产卵量 -T 单雌产卵量 ) / (S 单雌产卵量 -R 单雌产卵量 )×100%; RRC2=(S 卵孵化率 -T 卵孵化率 ) / (S 卵孵化率 -R 卵孵化率 )×100%; RRC3=(S 成虫寿命 -T 成虫寿命 ) / (S 成虫寿命 -R 成虫寿命 )×100%; Among them, T 单雌产卵量 T 卵孵化率 T 成虫寿命 S represents the arithmetic mean of single female egg production, the arithmetic mean of egg hatching rate, and the arithmetic mean of adult lifespan for the tested cassava variety. 单雌产卵量 S 卵孵化率 S 成虫寿命 R represents the arithmetic mean of the number of eggs laid per female, the arithmetic mean of the egg hatching rate, and the arithmetic mean of the adult lifespan of the highly susceptible mite reference species. 单雌产卵量 R 卵孵化率 R 成虫寿命 The arithmetic mean of single female oviposition, the arithmetic mean of egg hatching rate, and the arithmetic mean of adult lifespan are given for the high mite-resistant reference varieties. The relative resistance coefficient (RRC4) of the developmental stage index is calculated using the following formula: RRC4=(T 发育历期 -S 发育历期 ) / (R 发育历期 -S 发育历期 )×100%; Among them, T 发育历期 S is the arithmetic mean of the developmental duration of the new cassava variety to be tested. 发育历期 R is the arithmetic mean of the developmental period of a highly susceptible mite reference variety. 发育历期 This is the arithmetic mean of the developmental period of the high mite-resistant reference variety; The arithmetic mean of RRC1, RRC2, RRC3, and RRC4 is taken respectively, and the comprehensive relative resistance coefficient RRC of the tested cassava variety is calculated. avg ; RRC avg =(RRC1+RRC2+RRC3+RRC4) / 4 When the RRC avg A concentration of ≥80% is considered high mite resistance; 60% ≤ RRC avg If < 80%, it is considered anti-mite; the 40% ≤ RRC avg If the RRC is less than 60%, it is considered moderately mite-resistant; the above 20% ≤ RRC avg If < 40%, it is determined to be mite-susceptible; if the aforementioned RRC avg If the percentage is less than 20%, it is considered highly susceptible to mites; S2, Field Identification (1) Select the seed tubers of the new cassava variety to be tested, the reference variety with high mite resistance, and the reference variety with high mite susceptibility for field planting. After emergence, conduct an insect survey every 30 days until the cassava is harvested in the same year. (2) During each pest survey, plants were randomly selected from the new cassava variety to be tested, the highly mite-resistant reference cassava variety, and the highly mite-susceptible reference cassava variety. For each plant, 12 fully expanded leaves were taken from the upper, middle, and lower parts. The damage level, the number of leaves with the damage level, and the total number of mites on each fully expanded leaf were counted. The mite damage index I and the relative mite damage index RDI of the new cassava variety to be tested, the highly mite-resistant reference cassava variety, and the highly mite-susceptible reference cassava variety were calculated to determine the field mite resistance level of the new cassava variety to be tested. The mite infestation index, expressed as a percentage, is calculated using the following formula: I = [∑(leaf damage level × number of leaves with damage level) / (total number of leaves surveyed × highest representative value)] × 100%; The highest level represents a value of 4; The Relative Mite Infestation Index (RDI), expressed as a percentage, is calculated using the following formula: RDI = (I T -I S ) / (I R -I S ) × 100% Among them, I T I represents the mite infestation index of the tested variety. S As a reference variety for highly susceptible mites, I R The mite infestation index is used as a reference variety for high mite resistance. (3) Resistance determination: When RDI ≥ 80%, it is determined to be highly mite resistant; when 60% ≤ RDI < 80%, it is determined to be mite resistant; when 40% ≤ RDI < 60%, it is determined to be moderately mite resistant; when 20% ≤ RDI < 40%, it is determined to be susceptible to mites; when RDI < 20%, it is determined to be highly susceptible to mites. S3, Comprehensive Judgment When the indoor mite resistance level of the tested cassava variety is inconsistent with the field mite resistance level of the tested cassava variety, the field mite resistance level shall prevail; if reliable data cannot be obtained from field identification due to uncontrollable factors, the indoor mite resistance level of the tested cassava variety shall prevail. The highly mite-susceptible reference cassava variety is 'SC205', and the highly mite-resistant reference cassava variety is 'C1115'.

2. The method for identifying the mite resistance of a new cassava variety according to claim 1, characterized in that, The inoculation amount in step S1 (1) is 100 heads / leaf; the 1-day-old female adult mite is a 1-day-old female adult mite of the same size and development that has developed from the nymph.

3. The method for identifying the mite resistance of a new cassava variety according to claim 1, characterized in that, In step S2(1), the field identification is repeated in different years, with a minimum of 3 repetitions.

4. The method for identifying the mite resistance of a new cassava variety according to claim 1, characterized in that, The specific grading criteria for the damage level described in step S2 (2) are as follows: Level 0, no damage symptoms; Level 1, yellowish-white small spots occupying <25% of the leaf area; Level 2, yellowish-brown / rust-red spots occupying 26%~50% of the leaf area; Level 3, yellowish-brown / rust-red spots occupying 51%~75% of the leaf area, or leaves curling; Level 4, yellowish-brown / rust-red spots occupying ≥76% of the leaf area, leaves withered and falling off.

5. A novel high-density planting and pest control cultivation method for a new cassava variety, characterized in that, The new cassava varieties identified using the mite resistance identification method described in claims 1-4 are planted, and the specific steps are as follows: (1) Seed stem treatment: Select healthy, disease-free, undamaged, and plump seed stem segments of cassava varieties that are moderately or above resistant to mites as identified by the mite resistance identification method, and disinfect and dry the cut ends of the seed stem segments; (2) Site selection and land preparation and fertilization: Select a flat and well-drained site, deep plow the site and level it, then apply base fertilizer and plow and mix it evenly. (3) Dense planting: When the temperature is stable above 15℃ and the soil 0 cm to 20 cm layer is moist, the seedlings are planted in a single ridge equilateral triangle dense planting pattern; the seedlings are inserted obliquely into the soil, the soil is compacted, and the seedlings are managed according to the conventional field management plan. (4) Insect monitoring and scientific application of pesticides: After the cassava seedlings emerge, insect monitoring should be carried out every 10 to 15 days; when the average insect population density per single leaf exceeds 10 or the rate of damaged plants reaches 10%, biological agents should be sprayed for control. (5) Harvesting: 8 to 10 months after planting, when the lower leaves of the cassava plant begin to turn yellow and fall off, and the tubers stop expanding, the cassava can be harvested.

6. A novel high-density planting and pest control cultivation method for a new cassava variety according to claim 5, characterized in that, The length of the seed stem segment mentioned in step (1) is 15 cm to 20 cm, and 2 to 3 buds are retained; The disinfection method described in step (1) is to dip the cut end of the seed stem segment in wood ash, or soak it in a 1000-fold dilution of 50% carbendazim wettable powder for 3-5 minutes, and then let it dry before use.

7. A novel high-density planting and pest control cultivation method for a new cassava variety according to claim 5, characterized in that, The deep tillage depth mentioned in step (2) is 25 cm to 30 cm; The plots mentioned in step (2) should avoid being selected from plots where crops that are prone to spider mite infestation were previously planted; The base fertilizer mentioned in step (2) includes bio-organic fertilizer, phosphate fertilizer, and compound fertilizer, and the amount of base fertilizer used is per 667 m³. 2 Apply 500 kg to 800 kg of the bio-organic fertilizer, 50 kg of the phosphate fertilizer, and 30 kg to 40 kg of the compound fertilizer; The mass ratio of N, P2O5, and K2O in the compound fertilizer is 15:15:

15.

8. A novel high-density planting and pest control cultivation method for a new cassava variety according to claim 5, characterized in that, The single-ridge equilateral triangle dense planting pattern described in step (3) has a plant spacing of 60 cm; When planting the seed stem segment, the insertion depth is 1 / 2 to 2 / 3 of the length of the seed stem segment, with the bud facing upwards; The specific field management is as follows: before the cassava rows close, manual weeding is carried out according to the growth of weeds; 30-40 days after transplanting, when the seedlings of the new mite-resistant cassava variety grow to 20 cm-30 cm, topdressing with seedling fertilizer is applied in conjunction with weeding; during the tuber enlargement period 90-120 days after transplanting, topdressing with tuber enlargement fertilizer is applied; avoid waterlogging in the field throughout the entire growth period, and drain water in a timely manner after rain.

9. A novel high-density planting and pest control cultivation method for a new cassava variety according to claim 8, characterized in that, The topdressing of seedling fertilizer mentioned in step (3) is specifically applied per 667 m². 2 Apply 5-7 kg of urea and 10-15 kg of compound fertilizer as top dressing; the specific amount of top dressing for promoting growth is per 667 m². 2 Apply 10-15 kg of compound fertilizer and 10-15 kg of potassium fertilizer as top dressing; The mass ratio of N, P2O5, and K2O in the compound fertilizer is 15:15:

15.

10. A novel high-density planting and pest control cultivation method for a new cassava variety according to claim 5, characterized in that, The biological agent mentioned in step (4) is 1.8% abamectin emulsifiable concentrate at 5000 times dilution, 0.3% azadirachtin emulsifiable concentrate at 500-800 times dilution, or 1% matrine soluble concentrate at 500-800 times dilution; The spraying time mentioned in step (4) is on cloudy days and / or in the evening, and spraying is done once every 7 to 10 days, for a total of 2 sprayings.

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