Trichogramma chilonis attractant and application thereof in biological control

Abstract

The invention discloses a trichogramma chilonis attractant and an application of the trichogramma chilonis attractant in biological prevention and control. The pheromone comprises n-octane. The pheromone is used for improving the field control effect of trichogramma chilonis. The pheromone n-octane provided by the invention has a remarkable attraction effect on trichogramma chilonis, can effectively induce the trichogramma chilonis to parasitize target pests in the field, improves the field control effect, and makes contributions to synthesis of artificial pheromones and development of biological control.

Description

Technical Field

[0001] The present invention relates to the technical field of biological parasitism, and more specifically, to a Trichogramma chilonis attractant and its application in biological control. Background Art

[0002] In the field of biological control, using natural enemy insects to control pests is an environmentally friendly and sustainable method. Trichogramma chilonis, as an important egg parasitoid, has been widely used to control various agricultural pests, such as rice stem borers, oriental fruit moths, apple leafrollers, diamondback moths, cotton bollworms, pine caterpillars, etc. It has the advantages of rich resources, wide distribution, and significant pest control effect, and has become one of the most important natural enemy insects in the world, achieving remarkable results in the biological control of agricultural and forestry pests. Currently, Trichogramma has become an important natural enemy insect with the widest application range, the largest application area, and the most pest control targets in China.

[0003] However, the field application of Trichogramma chilonis in the prior art still has the following problems: low diffusion efficiency: after Trichogramma is released in the field, it is often affected by complex environments (such as wind, temperature, and humidity), resulting in uneven diffusion and difficulty in accurately locating pest eggs; large fluctuations in parasitism rate: affected by the concealment of host egg distribution and chemical pesticide residues, the parasitism rate of Trichogramma varies significantly in different fields, and the parasitism rate is relatively low; short effective duration: the adult lifespan of Trichogramma is short, and in the absence of continuous attracting signals, the control effect rapidly decreases with the extension of the release time. The prior art has tried to improve the effect by optimizing the release density, improving the carrier device, or adding plant-derived attractants, but there are the following limitations: high cost and poor stability of plant-derived attractants; chemically synthesized attractants have an attracting effect on non-target insects, which may interfere with the ecological balance.

[0004] Therefore, in view of the above problems, how to provide an attractant for Trichogramma chilonis to improve the field control effect is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a Trichogramma chilonis attractant, which includes n-octane.

[0006] Preferably, it further includes a solvent, and the solvent is an organic solvent.

[0007] Further, the organic solvent is one or more of ethanol, petroleum ether, or xylene.

[0008] The present invention also provides the application of the pheromone as described in the above technical solution, that is, the application of the pheromone in improving the field control effect of Trichogramma chilonis.

[0009] Preferably, the concentration of n-octane is 0.1 - 10 μg / μL.

[0010] As can be seen from the above technical solutions, compared with the prior art, the present invention discloses a Trichogramma chilonis attractant and its application in biological control, having the following beneficial effects:

[0011] The n-octane attractant provided by the present invention has a significant attracting effect on Trichogramma chilonis, can effectively induce Trichogramma chilonis to parasitize target pests in the field, and improve the parasitism rate, emergence rate and lifespan, contributing to the synthesis of artificial pheromones and the development of biological control. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0013] Figure 1 Selection response of Trichogramma chilonis to Corcyra cephalonica eggs sprayed with 1-pentadecene;

[0014] Figure 2 Taxis of Trichogramma chilonis to Corcyra cephalonica eggs sprayed with 2,5-dimethyltetrahydrofuran;

[0015] Figure 3 Selection response of Trichogramma chilonis to Corcyra cephalonica eggs sprayed with n-octane;

[0016] Figure 4 Selection response of Trichogramma chilonis to Corcyra cephalonica eggs sprayed with 2,4-di-tert-butylbenzene. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] The following will clearly and completely describe the technical solutions of the present invention in combination with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0018] The pheromone for Trichogramma chilonis includes n-octane and organic solvent ethanol, and the concentration of n-octane in ethanol is 0.1 μg / μL - 10 μg / μL.

[0019] EXPERIMENTAL EXAMPLE

[0020] TEST INSECTS

[0021] The Trichogramma chilonis used in the experiment was collected from the eggs of Grapholita molesta in the pear orchard in Yuncheng City, Shanxi Province. It was placed under the conditions of 26°C ± 1°C, RH 75% ± 5%, and a photoperiod of 15L:9D. After being propagated for multiple generations using the eggs of Corcyra cephalonica, it was used for the experiment. The Corcyra cephalonica used in the experiment was reared by mixing wheat bran, bean flour, corn flour, and white flour in proportion. Before the experiment, fresh eggs of Corcyra cephalonica (<24 h) were collected and inactivated under a 25W ultraviolet lamp for 45 min, and then evenly spread on clean cards (2.5 cm × 4 cm) coated with white latex to prepare the Corcyra cephalonica egg cards for parasitization by Trichogramma chilonis and kept in reserve.

[0022] The test volatile compounds are shown in Table 1:

[0023] Table 1 Purity and sources of the test standard compounds

[0024]

[0025]

[0026] Olfactory behavioral responses of Trichogramma chilonis to 4 volatile compounds

[0027] Female Trichogramma chilonis within 6 h after emergence were selected to conduct the olfactory behavioral response experiment. First, a "Y-shaped" glass tube (arm length 10 cm, included angle 75°, inner diameter 1 cm) was installed: both arms were connected to a flavor source bottle (100 ml conical flask with a nozzle), a glass rotameter, distilled water, and an activated carbon sampler. A 30W incandescent lamp was placed above, and the whole device was carried out in a closed and light-tight environment at a room temperature of 25°C ± 1°C and a relative humidity of 75% ± 5%.

[0028] Bioassay: 10 μl of the extract and the control solution (n-hexane) were respectively pipetted and dropped on filter papers with equal areas (r = 6 mm). After the solvent had volatilized, they were respectively placed in two conical flasks on the side walls of the Y-shaped olfactometer, and air was passed through for 5 min with an air flow rate of 300 ml / min in both arms; the selected single female was placed at the glass tube opening. When it climbed to 1 / 2 of the arm, air was passed through; within 5 min, when it climbed to 1 / 3 of any arm, it was recorded as an effective bee, otherwise it was ineffective. After every 10 bees were tested, the position was swapped, and they were washed with alcohol and then with distilled water, dried in an oven and reused. Each infochemical was divided into 3 concentration gradients, namely 0.1 μg / μl, 1 μg / μl, and 10 μg / μl. Each concentration was repeated 6 times, with 10 bees each time. The number of Trichogramma chilonis entering the treatment group and the control group in each group of experiments was respectively recorded. The attraction rate, relative attraction rate, and relative selection rate were calculated according to the formula.

[0029]

[0030] The criterion for judging whether the test insects are attracted is that the insects entering the odor source arm tube show a tendency towards the corresponding odor source, which is recorded as attraction. The value of the relative selective percentage (RSP) ranges from -100% to 100%. When RSP > 0, it indicates that the odor source is attractive to the test insects, and the larger the value, the stronger the attraction. When RSP < 0, it indicates that the test insects have an avoidance effect on the odor source, and the smaller the value, the stronger the avoidance effect.

[0031] Observation on the parasitic behavior of Trichogramma chilonis Ishii to 4 kinds of volatiles

[0032] Pre-mark a circular area with a diameter of 9 mm on the cardboard, and divide this area into 4 directions (3 o'clock, 6 o'clock, 9 o'clock and 12 o'clock directions). Fix 5 Corcyra cephalonica eggs in each direction, and use white latex to stick the eggs on the cardboard to ensure that the positions of the eggs are evenly distributed. Drop 0.2 μl of the control (n-hexane) and different concentrations of volatile semiochemicals (0.1 μg / μl, 1 μg / μl and 10 μg / μl) on the 5 eggs in each direction respectively to ensure that each egg is evenly covered. After the egg card is completely dried, put it into a finger tube (Φ = 2 cm, H = 8 cm), place the tube horizontally under the objective lens and adjust the light source so that the light can evenly irradiate the circular area of the egg card. Introduce a single female Trichogramma chilonis Ishii into the finger tube, and use a stereomicroscope and a video acquisition system to observe the behavioral responses of Trichogramma chilonis Ishii to Corcyra cephalonica eggs in real time. Mainly record the searching time, egg surface detection time, drilling and oviposition time, ending time and total time of Trichogramma chilonis Ishii in the circular area. ① Searching time: After the female wasp is introduced into the finger tube, it walks on the finger tube and around the egg card until the female wasp starts to tap the egg surface with its antennae. The parasitoid may also have additional behaviors: rest on the egg, groom itself and tap briefly (usually < 3 s), and then search again. ② Egg surface detection: After finding the host egg, the female wasp pats the egg surface around the egg with its antennae, from the moment the antenna of the female wasp touches the egg surface to the end of patting the egg surface. ③ Drilling and oviposition: When the female wasp finishes patting, it proves that it has found a suitable parasitic position. It will use the ovipositor to make a small hole on the egg surface, shake its body and insert it into the egg; from the moment the ovipositor extends to the moment the ovipositor is pulled out. ④ Ending: The time from when the ovipositor is pulled out to when the female wasp leaves the host egg to when the female wasp starts to search for another egg. This experiment includes 4 treatments, each treatment has 40 replicates, each replicate is observed for 30 min, and the Trichogramma chilonis Ishii egg card and finger tube are replaced after each group of observations is completed.

[0033] Parasitic results of Trichogramma chilonis Ishii to 4 kinds of volatiles: After the parasitic behavior ends, remove the Trichogramma chilonis Ishii in the above-mentioned finger tube. Mark the finger tube containing the parasitic egg card and place it in a constant temperature incubator. Record the number of host eggs after 5 days. After the Trichogramma chilonis Ishii emerges as adults, feed 10% sucrose water every day, and count the emergence rate and lifespan of the emerged wasps.

[0034] Data processing: The independent-samples t-test was used to analyze the parasitism behavior and results of Trichogramma chilonis on four volatiles and the attraction rate of the olfactory response of T. chilonis to four volatiles using SPSS Statistics 20 software. The chi-square test was used to analyze the selection response of T. chilonis to different host eggs, and Origin software was used to plot the graphs. One-way ANOVA was used to analyze the relative attraction rate and relative selection rate of T. chilonis to different host eggs. The significance level was set at P < 0.05.

[0035] Results and analysis:

[0036] The selection response of T. chilonis to Corcyra cephalonica eggs sprayed with four substances is shown in the appendix Figures 1-4 as shown, the olfactory response is shown in Table 2-5, the parasitism behavior is shown in Table 6, and the parasitism results are shown in Table 7.

[0037] Table 2 Olfactory response of T. chilonis to C. cephalonica eggs sprayed with 1-pentadecene

[0038]

[0039] Table 3 Olfactory response of T. chilonis to C. cephalonica eggs sprayed with 2,5-dimethyltetrahydrofuran

[0040]

[0041] Table 4 Olfactory response of T. chilonis to C. cephalonica eggs sprayed with n-octane

[0042]

[0043]

[0044] Table 5 Olfactory response of T. chilonis to C. cephalonica eggs sprayed with 2,4-di-tert-butylbenzene

[0045]

[0046] Note: The data in Tables 2-5 are mean ± standard error. * represents significant difference at P < 0.05, ** represents extremely significant difference at P < 0.01; no mark for no significant difference at P > 0.05.

[0047] Table 6 Parasitism behavior of T. chilonis on C. cephalonica eggs sprayed with four volatiles

[0048]

[0049]

[0050] Table 7 Parasitism results of T. chilonis on C. cephalonica eggs sprayed with four volatiles

[0051]

[0052]

[0053] In summary, the order of the effects of different volatiles on the parasitism results of Trichogramma chilonis is as follows: n-octane > 2,5-dimethyltetrahydrofuran > 1-pentadecene > 2,4-di-tert-butylbenzene. The effects of the type and concentration of volatiles on the behavior of Trichogramma chilonis are complex and diverse. When the concentration of n-octane is 10 μg / μl, the number and rate of parasitized eggs of Trichogramma chilonis on Corcyra cephalonica eggs are similar to those of the control group, but the emergence rate is significantly higher than that of the control group. Although n-octane does not significantly increase the parasitism rate at higher concentrations, it can effectively improve the emergence rate of Trichogramma, thereby enhancing its reproductive success rate. That is, n-octane has a significant attracting effect on Trichogramma chilonis, but the effects of different concentrations of n-octane are different. In practical applications, a reasonable concentration can be selected according to specific usage requirements.

[0054] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other. The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A Trichogramma chilonis attractant, characterized in that, It includes n-octane.

2. The Trichogramma chilonis attractant according to claim 1, characterized in that, It also includes a solvent, and the solvent is an organic solvent.

3. The Trichogramma chilonis attractant according to claim 2, characterized in that, The organic solvent is one or more of ethanol, petroleum ether or xylene.

4. Application of the Trichogramma chilonis Ishii attractant described in claims 1-3 in enhancing the field control effect of Trichogramma chilonis Ishii.

5. The application according to claim 4, characterized in that The concentration of the n-octane is 0.1-10 μg / μL.

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