CN116235825A - A method for prolonging the shelf life of egg parasitoids - Google Patents

Abstract

The invention discloses a method for prolonging the shelf life of parasitic bees. The method is to reproduce parasitic wasps by using fresh eggs of hosts stored at low temperature, and then store the parasitic wasps at low temperature. The method provides guidance for actual production: different breeding strategies are adopted according to the responses of different egg parasitic bees and host eggs thereof to low-temperature storage; when fresh and cold stored host eggs are used for breeding bees, different storage conditions should be adopted. The method can prolong shelf life as much as possible without affecting bee breeding quality and application effect, and is convenient for use and reduces bee breeding cost.

Description

Method for extending shelf life of egg parasitic wasp

Technical field:

The invention belongs to the field of biological control applications, and in particular relates to a method for extending the shelf life of egg parasitic wasps.

Background technology:

Egg parasitic wasps are a type of parasitic insect belonging to the order Hymenoptera. Adults lay eggs in host eggs, and larvae feed on egg yolk, pupate, and cause the death of the host. After the adults emerge from their shells, they bite through the host egg shells and go out to live freely. They are the main parasitic natural enemies of the egg stages of many pests and are widely used in the prevention and control of agricultural and forestry pests. However, in order to accumulate a sufficient number of egg parasitic wasps for field flooding release, flexible use, and cost reduction, there is a need to extend their shelf life as much as possible. Evaluating the low-temperature storage conditions of parasitic wasps and their hosts is one of the key aspects of quality control during large-scale breeding. It is very important to screen storage conditions that can not only maintain the freshness of host eggs but also be conducive to the reproduction of parasitic wasps.

Summary of the invention:

The purpose of the present invention is to provide a method for prolonging the shelf life of parasitic wasps and their host eggs, by which a sufficient number of high-quality parasitic wasps can be accumulated for highly efficient pest control by flooding release in the field.

The method for extending the shelf life of parasitic bees of the present invention is characterized in that the parasitic bees are propagated with fresh host eggs stored at low temperatures, and then the parasitic bees are stored at low temperatures.

Preferably, the fresh host eggs stored at low temperature for breeding parasitic wasps are fresh host eggs stored at 10°C for 5 days for breeding parasitic wasps.

Preferably, the low-temperature storage of the parasitic bees is to store the larval stage parasitic bees at 7° C. for 5 days.

Preferably, the host is Spodoptera frugiperda.

Preferably, the parasitic wasp is Telenomus remus.

The invention cold stores the fall armyworm eggs at 7° C. for 5 days, and cold stores the noctuid black egg wasp for 5 days, that is, the longest shelf life of the noctuid black egg wasp is 10 days.

The method of the present invention provides guidance for actual production: different breeding strategies are adopted according to the responses of different egg parasitic wasps and their host eggs to low-temperature storage; different storage conditions should be adopted when breeding bees with fresh and cold-stored host eggs. The method can extend the shelf life as much as possible without affecting the quality and application effect of breeding bees, facilitate use, and reduce the cost of breeding bees.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows the hatching rate of fall armyworm at different low temperatures and storage periods. The * on the column indicates that the Dunnett’S t-test showed significant difference (P≤0.05) from the control (27°C).

Figure 2 shows the biological parameters of the Spodoptera exigua using cold-stored Spodoptera exigua eggs as hosts under low-temperature storage. The * on the column indicates that the difference with the control (27°C) was significant (P≤0.05) after Dunnett’S t-test.

DETAILED DESCRIPTION

The following examples are provided to further illustrate the present invention, rather than to limit the present invention.

Embodiment 1:

The effects of low temperature storage on the hatching rate of Spodoptera frugiperda eggs were studied. Furthermore, the eggs of Spodoptera frugiperda with different cold storage treatments were used to breed Telenomus remus, and the optimal storage conditions for host eggs that can ensure the quality of host eggs and can be used for bee breeding were screened out.

This experiment set up two factors, with 3 repetitions for each treatment, namely: storage temperature: 4±1℃, 7±1℃, 10±1℃, 13±1℃, storage period: 3d, 5d, 7d, 9d.

Collect fresh egg masses of P. gracilis, select egg masses of basically consistent quality and store them in a low-temperature incubator at the corresponding temperature. After the set storage period, take them out of the feeding box and place them in a 27°C incubator for further culture. Observe 10 egg masses for each treatment, each with about 100 eggs, record the number of larvae hatched from each egg mass, and calculate the larval hatching rate. The control group is fresh egg masses, which are not cold stored.

Take about 100 egg masses of fall armyworm with basically the same quality after cold storage. Introduce the fully mated female black egg wasp of fall armyworm into the finger-shaped tube, put the prepared egg mass, take it out after parasitism for 24 hours, and continue to culture it in a 27℃ incubator until it ecloses. Observe and record the eclosion rate, eclosion amount, and female ratio. Ten egg masses are used for each cold storage temperature and storage period, and each treatment is repeated 3 times. The control group is inoculated with fresh egg masses.

Biological indicators and quality evaluation parameters:

The response of fall armyworm eggs to low temperature stress was investigated from the hatching rate. The fitness of cold-stored egg breeding was investigated from the emergence rate, emergence amount and female bee ratio of the black egg wasp of the fall armyworm.

The results are shown in Figure 1 and Table 1. Low temperature storage seriously affected the hatching rate of S. frugiperda eggs. Almost no S. frugiperda larvae hatched when stored at 10℃ for 5-9 days, 7℃ for 5-9 days, and 4℃ for 5-9 days. The longer the S. frugiperda eggs were stored at lower temperatures, the greater the impact on the biological parameters of S. frugiperda black egg wasp. However, the effect of breeding S. frugiperda black egg wasp with S. frugiperda eggs stored at 13℃ was not ideal. The number and rate of emergence were lower than those of host eggs stored at 10℃, and there was a significant difference with the control group. Using host eggs stored at 10℃ for 3 days, the emergence rate of S. frugiperda black egg wasp could reach 82.87%, and the proportion of females was 97.25%. However, the hatching rate of S. frugiperda cold storage under this condition was high, which was not conducive to the reproduction of S. frugiperda black egg wasp. The number and rate of emergence of Spodoptera exigua bred with host eggs stored at 10℃ for 5 days were not significantly different from those of the control group, which were 27.90 and 76.05%, respectively. Under this condition, the hatching rate of host eggs stored cold was close to 0. However, the values of various parameters of Spodoptera exigua parasitized on Spodoptera exigua eggs stored cold for 7 and 9 days were significantly different from those of the control group. Therefore, it was found that Spodoptera exigua eggs stored cold at 10℃ for 5 days were suitable for breeding Spodoptera exigua, and their breeding quality was not affected by the cold storage host.

Table 1 Biological parameters of Spodoptera exigua bred with cold-stored eggs of Spodoptera exigua

Note: The values in the table are mean ± standard error. Different capital letters after the same row of data indicate significant differences at the 0.05 level (Tukey’s test: P>0.05), and different lowercase letters after the same row of data indicate significant differences at the 0.05 level (Tukey’s test: P>0.05

Embodiment 2:

The effect of low temperature stress on the growth and development of Spodoptera exigua bred with fresh eggs of Spodoptera exigua was studied, and the optimal low-temperature storage conditions for Spodoptera exigua bred with fresh eggs of Spodoptera exigua were determined without affecting the breeding quality and application effect.

The experiment set up three factors: cold storage temperature: 4±1℃, 7±1℃, 10±1℃ and 13±1℃; the development days were set according to the development period of the noctuid black egg wasp: 2d (larval stage), 4d (prepupal stage), 6d (pupal stage), 8d (late pupal stage); storage period: 5d, 10d, 15d, 20d, 25d. The control group was non-cold storage treatment.

Select fresh single-layer eggs (about 80 eggs) of fall armyworm with basically the same quality. After the black egg bees of the fall armyworm emerge, put the egg mass in a ratio of 1:1, take it out after parasitism for 24 hours, put it in a glass tube, wait for it to develop to the set number of days, and then put it in a low-temperature incubator with the corresponding temperature for cold storage until the end of the set storage period. Take out the bee card and place it in an incubator under normal temperature conditions (27±1℃, 75±5%RH, L:D＝16h:8h) to continue to develop until emergence. Record the emergence rate, emergence amount, and female ratio, and repeat 3 times for each development day, with one bee card for each repeat. The control group is a non-cold storage treatment, and the bee card is placed in the above-mentioned normal temperature incubator for feeding until emergence.

Biological indicators and quality evaluation parameters:

The response of Spodoptera exigua to low temperature stress was investigated from the perspective of emergence rate (Table 2), emergence quantity (Table 3) and female bee ratio (Table 4).

The results showed that among the three factors, the extension of storage period and the decrease of cold storage temperature had a greater impact on the biological parameter values of Spodoptera frugiperda bred with fresh eggs of Spodoptera frugiperda. Comprehensive analysis showed that the treatments with no significant difference from the control group were storage at 4℃ for 5 days in the larval stage (4℃-5d-2d), storage at 7℃ for 5 days in the larval stage (7℃-5d-2d), storage at 10℃ for 10 days in the pupal stage (10℃-10d-6d), and storage at 13℃ for 15 days in the pupal stage (13℃-15d-6d). The best storage condition for Spodoptera frugiperda bred with fresh eggs was storage at 13℃ for 15 days when the eggs were 6 days old (pupa stage), which not only ensured the quality of Spodoptera frugiperda bred with fresh eggs, but also extended the shelf life.

Table 2. Emergence rate of Spodoptera exigua bred with fresh eggs of Spodoptera frugiperda under low temperature storage

Note: The values in the table are mean ± standard error. Different capital letters after the same row of data indicate significant differences at the 0.05 level (Tukey’s test: P>0.05), different lowercase letters after the same row of data indicate significant differences at the 0.05 level (Tukey’s test: P>0.05), * indicates that there is a significant difference between the Dunnett’S t-test and the control group.

Table 3. Emergence of Spodoptera exigua bred from fresh eggs of Spodoptera frugiperda under low temperature storage

Note: The values in the table are mean ± standard error. Different capital letters after the same row of data indicate significant differences at the 0.05 level (Tukey’s test: P>0.05), different lowercase letters after the same row of data indicate significant differences at the 0.05 level (Tukey’s test: P>0.05), * indicates that there is a significant difference between the Dunnett’S t-test and the control group.

Table 4. Female proportion of Spodoptera exigua bred from fresh eggs of Spodoptera frugiperda under low temperature storage

Note: The values in the table are mean ± standard error. Different capital letters after the same row of data indicate significant differences at the 0.05 level (Tukey’s test: P>0.05), different lowercase letters after the same row of data indicate significant differences at the 0.05 level (Tukey’s test: P>0.05), * indicates that there is a significant difference between the Dunnett’S t-test and the control group.

Embodiment 3:

The reproductive efficiency of the black egg wasp bred by cold-stored fall armyworm eggs under the dual stress of low temperature and host quality was studied, and the longest shelf life of the black egg wasp was determined without affecting the breeding quality and application effect.

Experimental setup: According to the comparison results of Example 1 and Example 2, the fall armyworm eggs with basically the same quality stored at 10°C for 5 days in Example 1 were selected to breed the black egg bees of Spodoptera frugiperda, and then the bees were stored at low temperature under the four cold storage conditions (development period-cold storage temperature-storage period: 2d-4°C-5d, 2d-7°C-5d, 6d-10°C-10d and 6d-13°C-15d) that were not significantly different from the control in the research results of Example 2. Each cold storage treatment was repeated 3 times, and each time 1 egg mass (about 100 eggs) was repeated, and the bees were inoculated at a ratio of 1:1, and the black egg bees of Spodoptera frugiperda that were bred from fresh eggs without cold storage were used as the control. The emergence rate, emergence amount, and female ratio were recorded.

Biological indicators and quality evaluation parameters:

The response of the noctuid black egg wasp to low temperature and host quality stress was examined in terms of emergence rate, emergence amount and female wasp ratio.

As shown in Figure 2, under the cold storage conditions of 2d-7℃-5d and 6d-13℃-15d, the proportion of females was higher than that of the control group, which was 99.02% and 100%. There was no significant difference between the other two treatments and the control group. Under the conditions of 2d-4℃-5d and 2d-7℃-5d, the number of eclosions was not significantly different from that of the control group, and the number of eclosions was the highest at 2d-7℃-5d, which was 71.67. The results showed that cold storage at 7℃ for 5 days in the larval stage (2d) is the best storage condition for the black egg wasp of the noctuid moth propagated by cold storage eggs. Therefore, the fall armyworm eggs are cold stored for 5 days, plus the black egg wasp of the noctuid moth is cold stored for 5 days, that is, the longest shelf life of the black egg wasp of the noctuid moth is 10 days.

The above experiments clearly show that low-temperature storage affects the quality of host eggs, which further affects the quality of parasitic wasps. This proves that under the dual stress of host quality and low-temperature storage, the longest shelf life of parasitic wasps is not measured by the storage period of host eggs plus the storage period of parasitic wasps bred with fresh eggs.

The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims.

Claims (5)

1. A method for extending the shelf life of parasitic wasps, wherein the parasitic wasps are bred from fresh eggs of a host stored at low temperature and then stored at low temperature.

2. The method of claim 1, wherein said low temperature storage of the fresh eggs of the host to reproduce the parasitic wasps is a cold storage of the fresh eggs of the host for 5d at 10 ℃.

3. The method of claim 1 or 2, wherein the low temperature storage of the parasitic wasps is carried out by chilling the parasitic wasps in larval stage at 7 ℃ for 5d.

4. The method of claim 1, wherein the host is spodoptera frugiperda (spodoptera frugiperda).

5. The method of claim 1, wherein the parasitic wasp is black egg wasp (Telenomus remus).

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