Method for inducing encarsia sophia to lay male eggs on hosts

Abstract

The invention relates to the field of pest control, in particular to a method for inducing encarsia sophia to lay male eggs on hosts. It is found for the first time that the n-heptadecane can serve as a host surface contact signal substance, the sex distribution decision of the light yellow encarsia avena is remarkably affected, breakthrough technical value is achieved, and the research blank of the chemical signal regulation and control of the male producing behavior of the heterodiscipline parasitic wasps is filled.

Description

Technical Field

[0001] The present invention relates to the field of pest control, and in particular to a method for inducing Encarsia sophia to produce male eggs on hosts. Background Art

[0002] Bemisia tabaci is an important pest, belonging to the family Aleyrodidae of the order Hemiptera, and has biological characteristics such as strong reproductive ability, fast population renewal rate, wide host range, and rapid development of drug resistance. Encarsia sophia is one of the dominant natural enemies of Bemisia tabaci, with good parasitic specificity and field adaptability. Its unique facultative self-replicating parasitic reproductive mode is as follows: mated female wasps lay fertilized eggs in Bemisia tabaci (primary host) bodies, which develop into female wasps; unmated female wasps superparasitize the bodies of other parasitoid individuals (secondary hosts) with unfertilized eggs, which develop into male wasps. This reproductive mode makes it difficult in artificial breeding and field release: that is, male wasps can only be developed from the superparasitism of secondary hosts by unmated female wasps. When the resources of secondary hosts are insufficient, the supply of male wasps is limited, which in turn affects the mating of female wasps and subsequent prevention and control efficacy. Therefore, there is an urgent need to develop a new method that does not rely on secondary hosts and can directly induce the production of male eggs on primary hosts to improve the artificial breeding efficiency and field release effect of Encarsia sophia.

[0003] Currently, there is no relevant guidance on chemically inducing female Encarsia sophia to directly produce male eggs on the primary host Bemisia tabaci. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for inducing Encarsia sophia to produce male eggs on hosts, and to solve the problems of low efficiency and limited resources in the traditional breeding method that relies on secondary hosts.

[0005] According to the method for inducing Encarsia sophia to produce male eggs in the specific embodiment of the present invention, the method includes the following steps: using a n-heptacosane solution to induce Encarsia sophia to produce male eggs on hosts.

[0006] According to the method for inducing Encarsia sophia to produce male eggs of the present invention, wherein the concentration of the n-heptacosane solution is 10 μg / mL.

[0007] According to the method for inducing Encarsia sophia to produce male eggs of the present invention, wherein the host is Bemisia tabaci.

[0008] According to the method for inducing Encarsia sophia to produce male eggs of the present invention, wherein the method includes the following steps:

[0009] Cultivate insect hosts;

[0010] Introduce female Encarsia sophia into the cultivated insect hosts to obtain newly emerged unmated female Encarsia sophia.

[0011] Drop the n - heptacosane solution onto the back of the nymphs of the insect host.

[0012] The present invention for the first time establishes a method for inducing female wasps of Encarsia sophia to directly produce male eggs on the primary host Bemisia tabaci by applying the specific contact compound n - heptacosane. This method gets rid of the dependence on secondary host resources in the traditional hyperparasitism mode, and realizes the directional induction and rapid reproduction of male wasps of Encarsia sophia without providing any secondary hosts, significantly improving the breeding efficiency and controllability.

[0013] The positive effects of the present invention are mainly reflected in the following aspects:

[0014] Improve the production efficiency of male wasps: By simply dropping n - heptacosane, virgin females can be induced to produce male offspring on the primary host, breaking through the reproductive limitation of the previous need for hyperparasitism on secondary hosts.

[0015] Optimize the breeding process and operation cost: Simplify the breeding process, without the need for the reproduction and synchronous development of secondary hosts, saving time and breeding resources, and reducing the operation difficulty and cost of artificial breeding.

[0016] Enhance the population regulation ability: Achieve controllable adjustment of the yield and timing of male wasps, facilitating quantitative proportioning according to the field release requirements, and improving the population dynamic regulation ability.

[0017] Enhance the stability of the prevention and control efficacy: By supplementing the supply of male wasps, ensuring that female wasps are fully mated, and avoiding the attenuation of the prevention and control efficacy caused by the scarcity of male wasps after field release, thereby continuously and effectively suppressing the population development of Bemisia tabaci.

[0018] Therefore, the present invention not only provides a new means for the large - scale artificial breeding of Encarsia sophia, but also provides technical support for the construction of an efficient and precise biological control system, with significant application and promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Showing the anatomical diagram of Bemisia tabaci nymphs dropped with n - heptacosane after being oviposited by Encarsia sophia;

[0020] Figure 2 Showing the male - producing rate of Encarsia sophia on Bemisia tabaci nymphs with and without dropping n - heptacosane and dropping n - hexane;

[0021] Figure 3 Showing the comparison of the male - producing rate of Encarsia sophia after dropping Bemisia tabaci nymphs with different concentration gradients of n - heptacosane. DETAILED DESCRIPTION OF THE INVENTION

[0022] In the following examples:

[0023] Host insect: Bemisia tabaci (Gennadius) of MEAM1;

[0024] Parasitic wasp: Encarsia sophia (Girault & Dodd);

[0025] Host plant: Gossypium spp. (“Xinke No. 8”), and potted cotton plants were cultivated until they had 3 - 4 true leaves for standby;

[0026] Agent: n - heptacosane (purity ≥ 98%), and it was dissolved in n - hexane to prepare 5 concentration gradient working solutions: 0.01, 0.1, 1, 10, 100 μg / mL. In addition, an n - hexane solvent control group and a blank control group were set up.

[0027] Example 1 Verification experiment on the induction of male - egg production in Encarsia sophia by n - heptacosane

[0028] 1.1 Preparation of host plants and Bemisia tabaci nymphs:

[0029] Potted cotton plants at the stage of growing 3 - 4 true leaves were selected as host plants. They were placed in an insect - rearing cage, and Bemisia tabaci adults were introduced, with 200 - 300 individuals per plant and the male - female ratio of about 1:1. After 24 h, all adults were removed, and the plants with eggs were continuously reared and cultivated in the greenhouse for 14 days until the Bemisia tabaci nymphs developed to the 3rd - 4th instar for standby. The culture conditions were set as temperature 26 ± 2°C, relative humidity 65% ± 5%, and light - dark cycle of 14:10 (L:D).

[0030] 1.2 Treatment of the inducer and grouping settings:

[0031] Third - instar Bemisia tabaci nymphs with consistent development and similar individual sizes were selected for the following three - group treatments: Blank control group: Bemisia tabaci nymphs without any treatment; n - hexane control group: n - hexane solvent was dropped at 2 μL / individual on the dorsal surface of each Bemisia tabaci nymph, and it was left to volatilize naturally for 10 minutes; n - heptacosane treatment group: n - heptacosane was dissolved in n - hexane to prepare a solution with a concentration of 1 μg / μL, and 2 μL of the solution was dropped on the body surface of each nymph, and it was left to volatilize naturally for 10 minutes. Each of the three groups had 5 replicates, each replicate was a host plant, and each cotton plant contained 30 ± 2 Bemisia tabaci nymphs.

[0032] 1.3 Introduction of female Encarsia sophia

[0033] Collect newly emerged (<24 h), unmated female Encarsia sophia, and introduce them into the above three groups of treated plants at a ratio of "3 female wasps: 30 nymphs" (i.e., 3 female wasps per plant). The wasp introduction time is 24 hours. The entire experiment is carried out in an artificial climate chamber with environmental conditions of temperature 26 ± 2 °C, relative humidity 65% ± 5%, and light-dark cycle of 14:10.

[0034] 1.4 Data collection and male production rate statistics

[0035] After 24 hours, dissect the whitefly nymphs under the above different treatments, observe whether there are parasitoid eggs in the nymphs, and count the oviposition rate of the whitefly nymphs. As Figure 1 and Figure 2 shown, statistical analysis shows that hentriacontane treatment can significantly induce female wasps to produce male eggs on primary hosts, and no parasitoid oviposition was observed in the blank group and the n-hexane control group, indicating that this male production phenomenon is induced by the contact signal of hentriacontane, rather than solvent stimulation or natural behavior.

[0036] Example 2 Effect of hentriacontane treatments at different concentrations on the male production rate of Encarsia sophia

[0037] 2.1 Host plants and insect sources

[0038] Use cotton plants (with 3 - 4 true leaves) and 3 - 4th instar B biotype whitefly nymphs with the same source and treatment method as in Example 1 as experimental hosts; use newly emerged, unmated female Encarsia sophia as female wasps to ensure that all experimental materials are of consistent development and reliable source.

[0039] 2.2 Preparation of hentriacontane solutions

[0040] Dissolve hentriacontane (n-heptacosane, purity ≥ 98%) in n-hexane to prepare 5 gradient working solutions with concentrations of 0.01 μg / mL, 0.1 μg / mL, 1 μg / mL, 10 μg / mL, and 100 μg / mL respectively. Each group of solutions is freshly prepared, and a dose of 2 μL / head is applied to the back of each whitefly nymph using a micropipettor.

[0041] 2.3 Experimental design and treatment

[0042] Set 5 replicates for each concentration, treat 1 plant for each replicate, and each single plant contains 30 ± 2 3rd instar whitefly nymphs. The treatment method is as follows:

[0043] Use a micropipettor to accurately and quantitatively drip each nymph;

[0044] After the liquid medicine naturally volatilizes for 10 minutes, transfer the plant into a wasp introduction cage;

[0045] Three newly emerged unmated female wasps were introduced into each plant, and the time for introducing the wasps was controlled for 24 hours;

[0046] The cultivation environment was the same as that in Example 1 to ensure data comparability.

[0047] 2.4 Data collection and statistical methods

[0048] After 24 hours, the nymphs of Bemisia tabaci under the above different treatments were dissected to observe whether there were parasitoid eggs in the nymphs, and the oviposition rate of Bemisia tabaci nymphs was counted.

[0049] The results showed that n - heptacosane had a weak induction effect on the production of male - producing eggs by female wasps at low doses; the best effect was achieved at a concentration of 10 μg / mL, and the male - producing rate reached 10%, which was significantly higher than that of other treatments (P < 0.01). As the concentration increased further, the induction effect decreased slightly, showing a characteristic of concentration - saturation response. It indicated that within a suitable concentration range, n - heptacosane could significantly induce female wasps of Encarsia sophia to produce male - producing eggs on primary hosts, and too high a concentration did not further enhance the effect ( Figure 3 ).

[0050] The above embodiments are only used to explain the technical solutions of the present application and do not limit the protection scope of the present application.

Claims

1. A method for inducing the parasitoid wasp Encarsia sophia to lay male eggs on hosts, characterized in that, The method includes the following steps: inducing the wasp Encarsia sophia to lay male eggs on insect hosts by using a n - heptacosane solution.

2. The method for inducing male egg production of Encarsia sophia on hosts according to claim 1, wherein The concentration of the n - heptacosane solution is 10 μg / mL.

3. The method for inducing the parasitoid wasp **Encarsia sophia** to lay male eggs on hosts according to claim 1, wherein, The insect host is Bemisia tabaci.

4. The method for inducing the parasitoid Encarsia sophia to lay male eggs on hosts according to claim 1, characterized in that, The method includes the following steps: Cultivating the insect host; Introducing female wasps of Encarsia sophia into the cultivated insect hosts to obtain newly emerged and unmated female wasps of Encarsia sophia; Dropping the n - heptacosane solution onto the dorsal surface of the nymphs of the insect host.

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