Encarsia formosa natural enemy attractant composition for controlling whitefly pests and its use

Abstract

The present invention belongs to the technical field of crop pest control, and relates to a natural enemy attractant of Encarsia formosa for the green prevention and control of whitefly pests and its use. The present invention provides a natural enemy attractant of Encarsia formosa, which is composed of a main component of the attractant and a solvent; the main component of the attractant is composed of pest-induced plant volatiles, healthy plant volatiles, nectar flower fragrance volatiles, and whitefly-related volatiles of pests. The present invention also simultaneously provides the use of the above-mentioned natural enemy attractant of Encarsia formosa: the attractant can significantly attract Encarsia formosa while repelling whitefly pests. The attractant of the present invention has good selectivity and can repel pests.

Description

Technical Field

[0001] The present invention belongs to the technical field of crop pest control, and relates to a natural enemy attractant of Encarsia formosa for the green prevention and control of whitefly pests and its use. Background Art

[0002] As one of the important means of integrated pest management, biological control has the characteristics of high efficiency, no pollution, safety for humans and livestock, and is beneficial to environmental protection. With the development of modern agriculture, it has received extensive attention, and natural enemy insects, as a special resource, are increasingly accepted by people. Developed countries began to develop the natural enemy insect industry since the 1960s. At present, about 150 natural enemies in the world are commercially produced and sold, and the main species are Trichogramma, Chrysopa, predatory mites, Orius, and ladybugs, etc., and certain social and economic benefits have been achieved.

[0003] The silverleaf whitefly (Bemisia tabaci Gennadius), also known as the cotton whitefly and sweet potato whitefly, has a very wide host range and can damage hundreds of crops such as ornamental plants, vegetables, legumes, cereals, and cotton, and is one of the important agricultural pests worldwide. The silverleaf whitefly has extremely strong reproductive ability, and the female silverleaf whitefly can lay hundreds of eggs on suitable host plants. Under suitable environmental conditions, the silverleaf whitefly has a short growth cycle and there is a phenomenon of generation overlap. Once it occurs, its population will increase sharply. The silverleaf whitefly not only sucks the plant sap, but also induces sooty mold and transmits virus diseases, thereby reducing crop yields and causing huge economic losses to agricultural production.

[0004] At present, various control measures are often used for the prevention and control of the silverleaf whitefly. Strict disinfection during seedling raising and timely removal of diseased plants and weeds in the field can eliminate eggs and adults and reduce the population of the silverleaf whitefly. In addition, chemical control and physical control measures can also be adopted. In the initial stage of the occurrence of the silverleaf whitefly, the use of chemical pesticides can reduce the population density of the silverleaf whitefly; installing a 50-mesh insect-proof net on the greenhouse wall can prevent the external silverleaf whitefly from entering the greenhouse. Coupled with the strong tropism of the silverleaf whitefly adults to yellow, the use of yellow sticky boards to trap and kill the silverleaf whitefly adults is a commonly used measure in greenhouses in China. In agricultural production, trap crops are planted to reduce its damage to the target protected crops, or intercropping with crops such as celery and leeks has a certain repellent effect on the silverleaf whitefly to a certain extent. For the silverleaf whitefly in the nymph stage, parasitic wasps such as Eretmocerus eremicus and Encarsia formosa can be used for control.

[0005] However, the control with chemical agents will enhance the resistance of Bemisia tabaci to pesticides and pose a great threat to the population of natural enemy insects. Hanging yellow sticky traps to trap Bemisia tabaci is only suitable for use in enclosed greenhouses, and using yellow sticky traps in the field cannot effectively control Bemisia tabaci; while dense insect-proof screens will affect the sufficient ventilation of the greenhouse and are extremely unfavorable to the growth of crops. Therefore, generally speaking, biological control can reduce the risks brought by the use of pesticides and reduce the human and material resources consumed by physical control. However, due to the small size of parasitic wasps and the search in the complex field environment of vegetation, it is urgent to study how to improve their search for host pests and the parasitism rate through the attracting effect.

[0006] There is a communication relationship mediated by chemical information substances among various species in nature, which is the medium for information exchange among different species. Plant volatiles are important olfactory cues for insects to locate host plants, find mates, food and habitats. At present, there have been many reports on the behavioral regulation of natural enemy parasitic wasps and pests by the volatiles of healthy plants and parasitic plants. As early as 1991, Takabayashi et al. found that the volatile (Z)-3-hexen-1-ol (leaf alcohol) of healthy corn leaves could attract Apanteles kariyai Watanabe; in 2021, Chen Wenbin found in the study of "The selectivity of Bemisia tabaci to three host plants and the effects of plant volatiles on its selection behavior" that cis-3-hexenyl acetate and linalool in the volatiles of Abutilon theophrasti had significant attracting effects on the pest Q-biotype Bemisia tabaci at the concentrations of 1, 10, and 100 μL / mL, while nonanal had an obvious repellent effect on the pest Bemisia tabaci at high concentrations. The analysis also found that different concentrations of compounds had different effects on Bemisia tabaci, indicating that the concentration of compounds would affect the selectivity of Bemisia tabaci. The three volatile components of linalool, cis-3-hexenyl acetate and nonanal, which have the function of regulating the tendency of Bemisia tabaci, can be used as potential attractant or repellent components, providing an important basis for implementing the "Push-Pull" control strategy of Bemisia tabaci to reduce its harm to crops. In 2008, Cao Fengqin et al. found that Bemisia tabaci showed a concentration-related positive tendency to compounds such as eucalyptol, limonene, myrcene and linalool in the volatiles of tomato, cabbage and pepper, while showed a negative tendency to eugenol, α-pinene, etc.; in 2019, the study by Di Guiqiu et al. found that β-pinene in the volatiles of pine leaves showed attracting activity to both the natural enemy Ascogaster reticulata and the male moth of the pest Laspeyresia zebeana. In short, the volatiles of non-host healthy plants play a certain role in the long-distance search and location of natural enemies.

[0007] Herbivore-induced plant volatiles have unique properties, such as discriminability, specificity, rhythmicity, systemicity, and groupness, which play the most significant role in attracting parasitoid wasps. For example, in 1990, Dicke et al. found that among the 4 effective components of the synomone induced by Tetranychus urticae in kidney beans, 3 were terpenoid compounds and the other was methyl salicylate. In 2010, Gao Yuanyuan et al. reported that methyl salicylate, methyl jasmonate, and linalool were important herbivore-induced volatiles in paddy fields and had significant attracting activities on the natural enemy Trichogramma ostriniae. In 2015, Takemoto et al. found that phellandrene and n-octanal produced by broad beans damaged by aphids could attract the parasitic natural enemy Aphidius ervi. In 2021, Ayelo et al. showed that Nesidiocoris tenuis could be attracted by the plant volatiles α-pinene, 3-carene, phellandrene, 3-isopropyl-6-methylene-1-cyclohexene, ocimene, β-caryophyllene, etc. induced after being damaged by Tuta absoluta and Trialeurodes vaporariorum. In the studies of Ayelo et al. in 2021 and Chan-shan C et al. in 2021, myrcene, 3-carene, β-caryophyllene, ocimene, and phellandrene induced after whitefly-damaged tomato plants could attract Encarsia formosa.

[0008] Volatiles of nectar plants also have a certain attracting effect on flower-visiting insects, and different promotion and improvement effects on the parasitism ability of parasitoid wasps after they tend to feed. Shang Lina et al. found in "Co-adaptation of Flower-visiting Insects and Nectar Plants in Changbai Mountain Area" that nectar plants had a significant attracting effect on flower-visiting insects, especially Hymenoptera insects (including Encarsia formosa), and preliminarily identified the volatile compounds of nectar plants as dihydroxyacetone (a polyhydroxy ketose, the simplest ketose), acetic acid, formic acid, cis-9,12-octadecadienoic acid, and phenol, etc.

[0009] Pheromones of pests, as well as volatiles from the feces and secretions of their hosts (also known as honeydew, which has a certain viscosity), etc. can serve as allomones, attracting parasitoid natural enemies and also regulating the behavior of pests. Boo, KS and Yang, JP (2000) found that Trichogramma chilonis would use the sex pheromones (Z)-11-hexadecyl acetate and (E)-12-tetradecyl acetate of Helicoverpa armigera to search for the eggs of Helicoverpa armigera; in 2022, Ayelo et al. reported that Encarsia formosa would be attracted by the honeydew of Trialeurodes vaporariorum. In 2019, Li Xiaowei et al. studied and found that Frankliniella occidentalis would release alarm pheromones when attacked by natural enemy insects, which had a repellent effect on other nymphs and adults of the same species and could also reduce the oviposition rate of female insects; in 2019, Yang Chaoxia et al. reviewed the application progress of the alarm pheromone [E]-β-farnesene (EβF) released by aphids when encountering natural enemy insects in aphid control. The study found that the alarm pheromone EβF not only had a repellent effect on aphids, but also could attract aphid predatory natural enemies such as ladybugs, syrphid flies, lacewings, and parasitic natural enemies such as parasitoid wasps, enabling them to locate aphids on plants, thereby reducing the aphid population and being suitable for the "push-pull" pest control strategy. In 2018, Li Xue et al. found that cis-9-octadecenal and cis-9-octadecenyl acetate identified from the hindgut extract of male Holotrichia oblita had an attracting effect on both male and female insects.

[0010] The body surface of the pest Bemisia tabaci is densely covered with a layer of wax powder, making it difficult for insecticides to penetrate into its body. It has strong resistance to drugs, and chemical control is difficult to achieve results. The adults of Bemisia tabaci are small and have two wings, and can fly and spread over long distances with the help of air currents. Coupled with its wide range of host plants, many generations occur annually, and its reproductive capacity is strong. Therefore, when Bemisia tabaci breaks out and causes damage, a single control measure cannot continuously and effectively control it, and multiple prevention and control methods should be combined. At present, the best green prevention and control method is to give full play to the pest control effect of natural enemies, and focus on the prevention and control of the nymph stage with weak activity to reduce the pest source base. The parasitoid wasps released artificially have weak ability to search for hosts in nature. Therefore, by studying the mechanism of natural enemy attraction, developing attraction technologies, rejuvenating and effectively multiplying egg parasitoid wasps to control Bemisia tabaci, it can just make up for the shortcomings of sex pheromone trapping and artificial release of wasps technologies in pest control to a large extent. And starting from this weak link in the life history of the nymph stage with very weak activity, using artificial release of natural enemies and natural enemy attraction technologies to cooperate with biological control will be a better choice to inhibit the population density of Bemisia tabaci. Therefore, protecting, releasing and naturally attracting natural enemy insects with a large parasitoid pest control effect on Bemisia tabaci can greatly reduce the emergence rate of pests, thereby reducing the damage of future generations and the control pressure. In China, the main parasitoid wasps of Bemisia tabaci are Eretmocerus hayati, Encarsia formosa, etc. Especially Encarsia formosa has been able to be artificially cultured on a large scale. Developing the attraction technology of the above parasitoid wasps using volatile odor substances in the vegetable garden habitat will play an active role in inhibiting the population density of Bemisia tabaci and protecting the high yield and quality of vegetables.

[0011] Patent CN111226931 B, "A lure for parasitoid wasps of ionone, preparation method and application", discloses a lure for parasitoid wasps of ionone, a preparation method and an application. In it, methyl salicylate, β-citronellol and ionone (especially β-ionone) were screened out, which have obvious attracting activities in the Y-tube test for Microplitis pallidipes. A lure for parasitoid wasps of ionone was prepared, and the source of the volatile substances is mainly plant volatiles;

[0012] Patent CN 111296474 B, "A lure for parasitoid wasps of citronellol, preparation method and application", uses citronellol (especially β-citronellol), with a single source, mainly plant volatiles, and the parasitoid wasp is Microplitis pallidipes;

[0013] Patent CN111226934 B, "A lure for parasitoid wasps of methyl salicylate, preparation method and its application", discloses a lure that mainly contains the plant volatile - methyl salicylate and has an attracting effect on parasitoid wasps;

[0014] Patent CN108770848 A, "A plant-derived lure for Encarsia formosa and its application", mainly uses different components of host plant volatiles, namely methyl salicylate, β-caryophyllene, (E)-β-ocimene, and β-myrcene, to prepare a plant-derived lure for the natural enemy Encarsia formosa. The source of the volatile components is relatively single, mainly from healthy plant volatiles and herbivore-induced plant volatiles. The reported volatile components have obvious attracting effects on the natural enemy Encarsia formosa, but the effects on the pests parasitized by the natural enemy have not been reported. Therefore, it is impossible to know whether it can attract both natural enemies and pests at the same time, or can repel pests while attracting natural enemies?

[0015] In natural habitats, parasitic natural enemy insects such as Encarsia formosa not only have a strong tendency towards healthy plant volatiles, herbivore-induced plant volatiles, and nectar plant volatiles, but also have a tendency towards pest-related information substances. In addition, they also have a tendency towards the information substances between natural enemy insects. Based on this, by analyzing and identifying compounds with significant attracting activities for the natural enemy insects of whitefly pests, Encarsia formosa, from multiple channels and sources in natural habitats, then screening out the compounds with attracting activities, and further optimizing the formulation, an artificial lure formulation is prepared. By slowly releasing it in a lure core, it can attract natural enemy insects, guide them to quickly search for and locate hosts, improve the parasitism rate of pests, and achieve green prevention and control. However, pests can also use the information substances in the habitat to complete their life activities. Therefore, when developing natural enemy lures, it is also necessary to consider testing the attracting and repelling effects on pests. Summary of the Invention

[0016] The problem to be solved by the present invention is to provide an attractant for Encarsia formosa, a natural enemy of whitefly pests, and its uses.

[0017] To solve the above technical problems, the present invention provides an attractant for Encarsia formosa (selective attractant for Encarsia formosa natural enemy): the attractant is composed of a main component of the attractant and a solvent;

[0018] The main component of the attractant is composed of pest-induced plant volatiles, healthy plant volatiles, nectar flower fragrance volatiles, and whitefly pest-related volatiles;

[0019] Pest-induced plant volatiles: healthy plant volatiles: nectar flower fragrance volatiles: pest-related volatiles = 1 to 100: 0.5 to 120: 0.5 to 120: 0.1 to 20 by volume ratio (preferably 5 to 10: 0.5 to 50: 0.5 to 50: 0.8 to 1, more preferably 5 to 10: 5 to 50: 6 to 50: 0.8 to 1).

[0020] As an improvement to the attractant for Encarsia formosa natural enemy of the present invention:

[0021] The pest-induced plant volatiles are any one of the following: methyl salicylate, methyl jasmonate, linalool, linalool oxide, (Z)-3-hexen-1-ol, 2-heptanone, tetradecane, hexadecane;

[0022] The healthy plant volatiles are any one of the following: α-caryophyllene, α-pinene, β-pinene;

[0023] The nectar flower fragrance volatiles are any one of the following: benzaldehyde, phenylacetaldehyde, benzyl alcohol, cis-3-hexen-1-yl acetate, benzyl acetate, 2,6-di-tert-butylphenol, phenol, dihydroxyacetone, cis-9,12-octadecadienoic acid;

[0024] The whitefly pest-related volatiles (kairomones) are composed of whitefly body surface volatiles / whitefly honeydew volatiles, specifically any one of the following: decane, undecane, tricosane, limonene.

[0025] As a further improvement to the attractant for Encarsia formosa natural enemy of the present invention: in the attractant; the volume concentration of the main component of the attractant is 1 to 10%.

[0026] As a further improvement to the attractant for Encarsia formosa natural enemy of the present invention: the main component of the attractant is composed of linalool: β-pinene: cis-3-hexen-1-yl acetate, decane with a volume ratio of 10: 5: 6: 0.8.

[0027] As a further improvement to the attractant for Encarsia formosa natural enemy of the present invention:

[0028] The attractant is composed of 10 μL of linalool, 5 μL of β-pinene, 6 μL of cis-3-hexen-1-yl acetate, 0.8 μL of decane, and 200 μL of n-hexane;

[0029] Alternatively, the attractant consists of 10 μL of linalool, 5 μL of β-pinene, 6 μL of leaf acetate, 0.8 μL of decane, and 978 μL of n-hexane.

[0030] The present invention also provides the use of the above-mentioned Encarsia formosa natural enemy attractant at the same time: the attractant can attract (significantly attract) Encarsia formosa and repel whitefly pests at the same time. That is, the attractant of the present invention has good selectivity and the function of repelling pests.

[0031] During the invention process of the present invention, it was found that: before the present invention, most reported studies only studied the attraction of a certain type of compound to the natural enemy Encarsia formosa alone, without systematically studying the combined effects of multiple components, and there was no verification of whether the attractant had an attracting or repelling effect on pests. For the natural enemy Encarsia formosa, in its chemical ecology positioning, the sources of chemical information substances sensed are diverse, mainly including a combination of compounds from pest-induced plant volatiles, healthy plant volatiles, nectar flower fragrance volatiles, pest-related volatiles, etc.

[0032] For Bemisia tabaci, before the present invention, there was no attractant formula developed and combined successfully for the natural enemy Encarsia formosa of Bemisia tabaci, closest to or most based on the natural field habitat environment, from healthy plant volatiles, pest-induced plant volatiles, nectar flower fragrance volatiles, pest-related volatiles (kairomones), etc. Therefore, there is an urgent need to develop an efficient natural habitat enemy attractant composition for controlling Bemisia tabaci suitable for the "push-pull" pest control strategy, which can selectively attract natural enemies and repel pests.

[0033] Therefore, in view of the problems existing in the current control of Bemisia tabaci, based on the chemical communication relationship among plants, pests, and natural enemies, the present invention uses different sources of compounds such as pest-induced plant volatiles, healthy plant volatiles, nectar flower fragrance volatiles, pest-related volatiles, etc. as the basis, and through exploring the effects of applying a single semiochemical and the mixture of multiple semiochemicals on the attraction effect of Encarsia formosa and field trials, a method for green pest control of Bemisia tabaci that is easy to use, low-cost, and has better control effect is developed. The attractant formula of the present invention is more scientific and reasonable, with strong selectivity. By continuously volatilizing the attractant in the field, it can better attract the natural enemy Encarsia formosa to parasitize pests to reduce the pest population, and at the same time, there is no risk of pesticide residue pollution, which can provide an effective method for green control of Bemisia tabaci and has great social and ecological benefits.

[0034] The Encarsia formosa attractant of the present invention has the following technical advantages:

[0035] 1. Based on the chemical communication relationship among plants, pests, and natural enemies in natural habitats, the present invention rationally blends pest-related volatiles, nectar flower fragrance volatiles, healthy plant volatiles, pest-induced plant volatiles, etc., and adjusts the blending ratio according to the functions of the compounds, achieving a good effect of attracting Encarsia formosa. It can overcome the defects that the components of mutual benefit substances vary greatly and have a poor guiding effect on natural enemies to locate pests at close range, and can also overcome the disadvantage that kairomones have a poor effect on natural enemies searching for pests at long distances. The blended attractant has a good attracting effect and a certain pest repellent effect both in laboratory and field tests, and has good repeatability and high stability.

[0036] That is, the formula source of the volatile composition of the present invention is relatively close to the real state in natural habitats: there are pest-induced plant volatiles, healthy plant volatiles, nectar flower fragrance volatiles, and pest-related volatiles.

[0037] 2. The attractant can significantly attract Encarsia formosa and repel whitefly pests at the same time. The present invention can not only selectively attract the natural enemy Encarsia formosa, but also repel whitefly pests at the same time. That is, when artificially reared natural enemies are released in the field, it will not attract all the nearby pests.

[0038] In summary, the present invention studies the attracting effect of volatiles on Encarsia formosa from the aspect of olfactory behavior, and screens out different composition formulas. The formulas have a good selective attracting effect on the natural enemy Encarsia formosa through indoor and field tests, and can be used for the biological control of whitefly pests. The above-mentioned optimized attractant for Encarsia formosa natural enemy after compounding can have a good attracting effect on Encarsia formosa, an important natural enemy of whitefly pests, and has a repellent effect on whitefly pests, with high control efficiency, low cost, environmental friendliness, safety for humans and livestock, and natural environmental protection. That is, the present invention has screened out a compound formula with significant attracting activity for Encarsia formosa, and improved the parasitism rate of Encarsia formosa on Bemisia tabaci nymphs and the biological control effect in the natural field environment.

[0039] The actual usage method of the attractant for Encarsia formosa natural enemy of the present invention in the field is as follows: after finding nymphs during the high-incidence period of Bemisia tabaci in the field, take 20 μL of the attractant for Encarsia formosa natural enemy and place it in a rubber head lure core near the Bemisia tabaci nymphs, which is one treatment; set up more than a dozen repetitive treatments in different areas to attract Encarsia formosa to lay eggs in the Bemisia tabaci nymphs, thereby reducing the number of hatched pest eggs and reducing the pest source base. Detailed implementation mode

[0040] The present invention will be further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto:

[0041] Example 1: An attractant for Encarsia formosa

[0042] Dissolve 10 μL of linalool, 5 μL of β-pinene, 6 μL of leaf acetate, and 0.8 μL of decane in 980 μL of n-hexane, and mix well.

[0043] Comparative Example 1-1: Compared with Example 1, the attractant only contains volatile substances from healthy plants:

[0044] Dissolve 5 μL of β-pinene in 980 μL of n-hexane and mix well.

[0045] Comparative Example 1-2: Compared with Example 1, the attractant only contains volatile substances from pest honeydew (decane):

[0046] Dissolve 0.8 μL of decane in 980 μL of n-hexane and mix well.

[0047] Comparative Example 1-3: Compared with Example 1, the attractant only contains volatile substances from plants induced by pests:

[0048] Dissolve 10 μL of linalool in 980 μL of n-hexane and mix well.

[0049] Example 2: A parasitoid wasp attractant

[0050] Mix 10 μL of methyl salicylate, 5 μL of β-pinene, 6 μL of leaf acetate, 1.0 μL of decane, and 980 μL of n-hexane well.

[0051] Comparative Example 2-1: Compared with Example 2, the volatile substances from plants induced by pests, methyl salicylate, are not used:

[0052] Dissolve 5 μL of β-pinene, 6 μL of leaf acetate, and 1.0 μL of decane in 980 μL of n-hexane.

[0053] Comparative Example 2-2: Compared with Example 2, the healthy plant volatile substance β-pinene is not used:

[0054] Dissolve 10 μL of methyl salicylate, 6 μL of leaf acetate, and 1.0 μL of decane in 980 μL of n-hexane.

[0055] Comparative Example 2-3: Compared with Example 2, the volatile substance from pest honeydew, decane, is not used:

[0056] Dissolve 10 μL of methyl salicylate, 5 μL of β-pinene, and 6 μL of leaf acetate in 980 μL of n-hexane.

[0057] Example 3: A parasitoid wasp attractant

[0058] Mix 5 μL of linalool, 10 μL of β-pinene, 6 μL of leaf acetate, 1.0 μL of decane, and 980 μL of n-hexane well.

[0059] Comparative Example 3-1: Compared with Example 3, the content of pest-induced plant volatiles was reduced:

[0060] 0.5 μL of linalool, 10 μL of β-pinene, 6 μL of leaf acetate, and 1.0 μL of decane were dissolved in 980 μL of n-hexane.

[0061] Comparative Example 3-2: Compared with Example 3, the content of healthy plant volatiles was reduced;

[0062] 5 μL of linalool, 0.1 μL of β-pinene, 6 μL of leaf acetate, and 1.0 μL of decane were dissolved in 980 μL of n-hexane.

[0063] Comparative Example 3-3: Compared with Example 3, the content of pest honeydew volatiles was reduced;

[0064] 5 μL of linalool, 10 μL of β-pinene, 6 μL of leaf acetate, and 0.01 μL of decane were dissolved in 980 μL of n-hexane.

[0065] The above Examples 1 to 3 and Comparative Examples 1-1 to 3-3 were subjected to a selectivity behavior test of the attractant on Encarsia formosa according to the method described in Experiment 1 below, and the results are shown in Table 1 below:

[0066] Experiment 1: The selection behavior of Encarsia formosa for each attractant combination was determined by a Y-tube olfactometer, which can refer to Experiment 1 of CN113383774B:

[0067] After the Y-tube olfactometer device was installed, 20 μL of each attractant formulation composition solution was dropped onto the folded filter paper (5 cm × 3 cm). After waiting for 1 min for the solvent to evaporate, the filter paper was placed into the odor source bottle (odor bottle) of the Y-tube olfactometer, and the odor source bottle on the other side was used with an equal amount of solvent as a control. The power was turned on, and the air flow passed through the activated carbon and then through the moistened distilled water bottle, and then entered the odor source bottle with the compound through the glass rotameter. The odor in the odor source bottle was brought to the two arms of the Y-tube. After ventilation for 1 min, adult Encarsia formosa were introduced one by one from the entrance of the Y-tube. The flow rate of the rotameter was 240 mL / min throughout the experiment.

[0068] After introducing *Encarsia formosa*, observe and record their behavioral responses within 5 minutes. If *Encarsia formosa* enters the compound arm or the solvent control arm and exceeds 1 / 3 of the length of the Y-tube arm, or does not turn around within 10 seconds after entering the arm, it is recorded as choosing that arm, that is, *Encarsia formosa* prefers the compound in that arm; if *Encarsia formosa* does not enter any arm within 5 minutes after being introduced into the Y-tube, or comes out from the entrance of the Y-tube, it is recorded as having no response. The same three Y-tubes are used throughout the experiment. After testing 10 *Encarsia formosa* with each Y-tube, clean it with 95% ethanol, dry it, then swap the compound and control odor source bottles and connect them to the two arms of the Y-tube, and replace the filter papers with the compound and the solvent, and continue to test another ten insects to eliminate experimental errors caused by the instrument, light, and the preference of insects for direction, etc. That is to say, each Y-tube is used twice, that is, each Y-tube tests 20 insects, and a total of 60 insects are tested for each concentration. The *Encarsia formosa* used in the experiment are all adults within 1 day after eclosion, and each insect is used only once.

[0069] In the Y-tube olfactometer behavioral determination experiment, the number of *Encarsia formosa* choosing the compound arm and the number of *Encarsia formosa* choosing the solvent control arm are analyzed by the chi-square goodness-of-fit test (χ2 test). This test is based on the null hypothesis that the ratio of the number of insects choosing the compound and the solvent control is 1:1. Data analysis and processing do not include the number of *Encarsia formosa* that have no obvious preference for the compound or the solvent, that is, the number of insects with no response. IBM SPSS Statistics 23 software is used for statistical analysis. If the number of *Encarsia formosa* choosing the two arms is tested by the χ2 test, P < 0.05 represents a significant difference, and P < 0.01 represents a highly significant difference.

[0070] Table 1 Attraction effect of Examples 1-3 and Comparative Examples 1-9 on *Encarsia formosa*

[0071]

[0072] Note: NV represents the number of *Encarsia formosa* choosing the volatile arm, and the selection rate V represents the proportion of *Encarsia formosa* choosing the volatile arm; NC represents the total number of *Encarsia formosa* choosing the blank control arm, and the selection rate C represents the proportion of *Encarsia formosa* choosing the blank control arm. Selection rate V = [NV / (NV + NC)] × 100%, selection rate C = [NC / (NV + NC)] × 100%. The *Encarsia formosa* with no response are not included in the data processing. χ 2 is the chi-square test value, df represents the degrees of freedom, the p-value represents the significance level, p < 0.05 represents a significant difference, and p < 0.01 represents a highly significant difference.

[0073] Example 4: Set attractants with the following formulations respectively:

[0074] Combination 1: 5 μL of linalool, 5 μL of β-pinene, 6 μL of leaf acetate, 0.8 μL of decane were dissolved in 980 μL of n-hexane. Combination 2: 5 μL of linalool, 50 μL of β-pinene, 6 μL of leaf acetate, 0.8 μL of decane and 980 μL of n-hexane.

[0075] Combination 3: 10 μL of linalool, 5 μL of β-pinene, 10 μL of leaf acetate, 0.8 μL of decane were dissolved in 980 μL of n-hexane. Combination 4: 10 μL of linalool, 0.5 μL of β-pinene, 50 μL of leaf acetate, 0.8 μL of decane were dissolved in 980 μL of n-hexane. Combination 5: 10 μL of linalool, 50 μL of β-pinene, 0.5 μL of leaf acetate, 0.8 μL of decane and 980 μL of n-hexane were mixed evenly.

[0076] Combination 6: 10 μL of linalool, 5 μL of β-pinene, 10 μL of leaf acetate, 0.8 μL of decane were dissolved in 980 μL of n-hexane. Combination 7: 10 μL of linalool, 5 μL of β-pinene, 50 μL of leaf acetate, 5 μL of decane were dissolved in 980 μL of n-hexane. Combination 8: 10 μL of linalool, 5 μL of β-pinene, 0.5 μL of leaf acetate, 50 μL of decane and 980 μL of n-hexane were mixed evenly.

[0077] Detection was carried out according to the above experiments.

[0078] Table 2 Attraction effects of each preferred composition 1-9 on Encarsia formosa

[0079]

[0080] As can be seen from Table 2, the attractant combinations 1-8 all have good attraction activities on Encarsia formosa, and the attractants 1-8 are all compounded from pest-induced plant volatiles, healthy plant volatiles, nectar flower fragrance volatiles, pest-related volatiles, etc. This result further shows that in the Encarsia formosa attractant, pest-induced plant volatiles, healthy plant volatiles, nectar flower fragrance volatiles, and pest-related volatiles are indispensable, and only the compounds within a suitable range are closer to the real environment in the natural habitat, so as to better attract Encarsia formosa.

[0081] Example 5: Repellent effect of the attractant on the pest Bemisia tabaci

[0082] The following attractant formulations were set respectively:

[0083] Attractant 1 (Example 1): 10 μL of linalool, 5 μL of β-pinene, 6 μL of leaf acetate, 0.8 μL of decane were dissolved in 980 μL of n-hexane.

[0084] Lure 2: Dissolve 5 μL of β-pinene, 6 μL of leaf acetate, and 0.8 μL of decane in 980 μL of n-hexane.

[0085] Lure 3: Dissolve 10 μL of linalool, 5 μL of β-pinene, and 0.8 μL of decane in 980 μL of n-hexane.

[0086] Lure 4: Dissolve 10 μL of linalool, 5 μL of β-pinene, and 6 μL of leaf acetate in 980 μL of n-hexane.

[0087] The following experiment was conducted.

[0088] Experiment 2. Four-arm olfactometer test of the avoidance behavior of the pest Bemisia tabaci to each lure combination

[0089] It was measured using a four-arm olfactometer (Shanghai Hefan Instrument Co., Ltd., Shanghai), with a diameter of 150 mm, a depth of 30 mm, and a total thickness of 80 mm, placed in a dark room, and the room temperature was 26 ± 2 °C. It was connected with medical rubber tubes in the order of air pump, distilled water bottle, activated carbon tube, glass rotor flowmeter, odor source bottle, and four-arm olfactometer. The air flow entered the air inlet through the air pump, passed through the washing bottle to remove impurities, and was dried by the activated carbon in the activated carbon tube. The air flow rate was controlled at 300 mL / min.

[0090] Before the experiment, adult B. tabaci of random gender and age were starved for 2 h. After connecting the four-arm olfactometer, 10 μL of the formula (lure) and three 10 μL of n-hexane were respectively placed on four filter papers of the same size. After the solvent evaporated for 30 s, they were respectively put into four odor source bottles. Turn on the power supply, let the air flow pass through the activated carbon and flowmeter, and then pass through the moist distilled water bottle and odor source bottle, and then the air flow with different concentrations of compounds entered the four-arm olfactometer to form a stable odor field, and the air flow rate was controlled at 300 mL / min. An adult B. tabaci that had been starved was introduced through the central small hole of the four-arm olfactometer, and it was given 1 min to adapt to the odor field. After 1 min, the timing started. Observe the behavioral responses of adult B. tabaci in the next 12 min, and record the time that adult B. tabaci stayed in the four odor fields. If the introduced adult B. tabaci remained motionless for 3 consecutive minutes from the start of timing, it was regarded as having no response. In the experiment, the four odor sources were randomly connected to each arm of the four-arm olfactometer, and the four-arm olfactometer was rotated clockwise by 90° every 3 min to exclude the influence of light and direction on the results. After each insect was tested, the four-arm olfactometer was cleaned with 75% ethanol and then placed in an oven to dry. The filter paper with the odor source was replaced and a new adult B. tabaci was introduced to continue the measurement. Each compound was repeated 12 times. Each adult B. tabaci was only used once in the experiment. The data results of the time that B. tabaci stayed in each odor area were analyzed by one-way ANOVA using SPSS Statistics 23.

[0091] Table 3 Repellent effects of attractant formulations on Bemisia tabaci

[0092]

[0093]

[0094] Note: The residence time (s) of Bemisia tabaci in the four odor zones is presented as the mean ± standard error. CK represents the solvent control n-hexane. After converting the residence time of Bemisia tabaci in each odor zone to the proportion of the total time (12 min) allowed for the insects to make a choice, logarithmic transformation was performed, and multiple comparisons were made using Tukey's HSD. p < 0.05 indicates significant differences and is represented by different letters. 10 Conversion was performed, and multiple comparisons were made using Tukey's HSD. p < 0.05 indicates significant differences and is represented by different letters.

[0095] As can be seen from Table 3, when any one source of compound is missing from the formulation, it has no repellent activity against Bemisia tabaci. When the formulation contains healthy plant volatiles, herbivore-induced plant volatiles, and pest honeydew volatiles simultaneously, the repellent effect against Bemisia tabaci can be enhanced (the residence time is significantly shorter, indicating a repellent effect). This shows that the combined use of compounds in the habitat may have a synergistic effect, which is not only reflected in attracting natural enemy insects but also in repelling pests.

[0096] Example 6: Field attraction effect of attractant on Encarsia formosa and field repellent effect on Bemisia tabaci

[0097] Field attraction experiment of attractant on Encarsia formosa

[0098] Field experiments were conducted to test the actual attracting effect of the obtained better attractant formulations on Encarsia formosa and the repellent activity against the pest Bemisia tabaci. Methyl salicylate has an attracting effect on a variety of natural enemy insects and is widely used as a commercial product, so it was used as the positive control for this field experiment. Each compound was formulated into different attractant formulations A, B, and C according to the volume ratio. The field application concentration needed to be appropriately increased, and n-hexane was reduced to 200 μL. There was also a blank solvent control of n-hexane, that is, there were a total of 5 treatments in the experiment. About 200 μL of the formulated solution of each treatment was dropped into the rubber head lure carrier. After the solvent evaporated, each formulated compound was adsorbed in the rubber head lure, and the effective period was about 15 days. The field trapping experiment of Encarsia formosa was carried out in a tomato field of a vegetable and fruit professional cooperative in Liangzhu Town, Yuhang District, Hangzhou City (30.38°N, 120.05°E) in June. The white sticky board was placed in the triangular insect trap and assembled. The rubber head lure was suspended in the center of the triangular insect trap with a wire in the middle, and marks were made on the insect trap with a marker pen and label paper. Due to the open field, after expanding the formulated concentration of the indoor attracting effect, 200 μL was taken with a pipette and dropped into the lure, and then the insect trap was randomly suspended in the upper-middle part of the tomato plant with a wire. The distance between two insect traps was 8 m, and the formulations in the lures of the insect traps were random. Four Encarsia formosa cards were suspended in the middle of two insect traps. Each card had about 200 Encarsia formosa, and the hatching rate was 70% - 80%. To reduce the number of Encarsia formosa escaping, no cards were suspended within a range of 2 m from the field margin. The experiment was set with 4 replicates. After the insect traps and cards were suspended in the field for 7 days, the insect traps were retrieved, and the number of Encarsia formosa and Bemisia tabaci stuck on each sticky board was counted with a stereomicroscope in the laboratory.

[0099] Field repellency experiment against Bemisia tabaci:

[0100] The formulations in the indoor primary screening that had a significant attracting activity on Encarsia formosa and an attraction rate exceeding 60% were verified outdoors to see if they had a repellent effect on Bemisia tabaci. Utilizing the strong tendency of adult Bemisia tabaci towards yellow, the field repellency of the test formulations was tested. If the formulation had a repellent activity against Bemisia tabaci, the number of Bemisia tabaci on the yellow board would be less than that of the blank control. During the high-incidence period of Bemisia tabaci, yellow sticky boards were suspended in the vegetable field at a height of 30 cm from the eggplant. The plastic paper on the same side of the yellow board was torn off, and the torn side was suspended with a rubber head using a wire. 200 μL of the formulated solution was dropped into the rubber head, and the distance between the yellow boards was 5 m. Each formulation was repeated three times. After the yellow boards were suspended for two days, the yellow sticky boards were retrieved, and the number of Bemisia tabaci stuck on each yellow board was counted.

[0101] Composition of the field experiment formulations:

[0102] Formulation A (compared with Example 1, the concentration of the main attractant component was increased): Linalool: β-Pinene: Leaf acetate: Decane:

[0103] n-Hexane = 10:5:6:0.8:200;

[0104] Formulation B (compared with Example 2, the concentration of the main components of the attractant is increased): Methyl salicylate: β-Pinene: cis-3-Hexen-1-yl acetate:

[0105] Decane: n-Hexane = 10:5:6:1:200;

[0106] Formulation C (compared with Example 3, the concentration of the main components of the attractant is increased): Linalool: β-Pinene: cis-3-Hexen-1-yl acetate: Decane:

[0107] n-Hexane = 5:10:6:1:200;

[0108] Comparative Formulation D: β-Pinene: cis-3-Hexen-1-yl acetate: Decane: n-Hexane = 5:6:0.8:200;

[0109] Comparative Formulation E: Linalool: β-Pinene: Decane: n-Hexane = 10:5:1:200;

[0110] Comparative Formulation F: Linalool: β-Pinene: Benzyl acetate: n-Hexane = 10:5:6:200;

[0111] Comparative Formulation G: Linalool: β-Pinene: Benzyl acetate: Tricosane: n-Hexane = 10:5:6:1:200;

[0112] CK+: Methyl salicylate: n-Hexane = 10:200;

[0113] CK-: n-Hexane = 200.

[0114] This experiment recorded the change process of the number of Encarsia formosa attracted in the field and the number of Bemisia tabaci adhered during the experimental period. The average number detected on a single sticky board for different treatments is shown in Table 4.

[0115] Table 4. Average trapping numbers of different attractant treatments in the field (unit: number / single board)

[0116]

[0117] In summary, the present invention screened out a preferred natural enemy Aphididae attractant formula through indoor and field tests. That is, linalool: β-pinene: phytol acetate: decane: n-hexane is compounded at a volume ratio of 10:5:6:0.8:200, which has the best selectivity, good attracting effect on Aphididae, and significant effect on pest avoidance. The formula of the present invention is the first natural enemy attractant of Aphididae developed for the pest Bemisia tabaci. The attractant has been confirmed by field tests to have a good biological control effect on Bemisia tabaci. Compared with the existing literature, the source of the formula of the present invention is more extensive, and it can more effectively simulate the environment of nature. It can be used in coordination with the release of artificially reared Aphididae to develop attractant technology, rejuvenate and effectively expand the egg parasitic bees to control Bemisia tabaci, and can make up for the shortcomings of sex inducement and artificial bee release technology in pest control to a large extent. Therefore, the formula of the present invention is more green and safe during use, and has a synergistic effect on the biological control of Bemisia tabaci.

[0118] Finally, it should be noted that the above examples are only some specific embodiments of the present invention. Therefore, the present invention is not limited to the above embodiments, and there are many variations. All variations that can be directly derived or associated with the content disclosed by a person skilled in the art should be considered as the protection scope of the present invention.

Claims

1. Encarsia formosa natural enemy attractant, characterized in that: The attractant consists of a main component of the attractant and a solvent; The main component of the attractant consists of pest-induced plant volatiles, healthy plant volatiles, honey-source flower fragrance volatiles, and pest whitefly-related volatiles; The volume ratio of pest-induced plant volatiles : healthy plant volatiles : honey-source flower fragrance volatiles : pest-related volatiles = 5-10:5-50:6-50:0.8-1; The volatiles induced by pests in plants are linalool, and the volatiles of healthy plants are β- pinene, the volatiles of honey-source flower fragrance are cis-3-Hexenyl acetate, and the volatiles related to the pest whitefly are decane.

2. The Encarsia formosa natural enemy attractant according to claim 1, wherein: In the said attractant, the volume concentration of the main component of the attractant is 1-10%.

3. The Encarsia formosa natural enemy attractant according to claim 1 or 2, characterized in that: The main components of the attractant consist of linalool, β- pinene, leaf acetate, and decane with a volume ratio of 10:5:6:0.

8.

4. The Encarsia formosa natural enemy attractant according to claim 3, characterized in that: The attractant consists of 10 μL of linalool, β- 5 μL of pinene, 6 μL of cis-3-hexenyl acetate, 0.8 μL of decane and 200 μL of n-hexane; Alternatively, the attractant consists of 10 μL of linalool, β- 5 μL of pinene, 6 μL of cis-3-hexenyl acetate, 0.8 μL of decane and 980 μL of n-hexane.

5. Use of the Encarsia formosa natural enemy attractant according to any one of claims 1 to 4, characterized in that: The said attractant can attract Encarsia formosa and simultaneously repel the pest Bemisia tabaci.

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