CN118340175A - A method for controlling red imported fire ants by combining insect pathogenic nematodes with chemical pesticides - Google Patents

Abstract

The present invention provides a method for controlling red fire ants by combining insect pathogenic nematodes with chemical pesticides, wherein the insect pathogenic nematodes are used in combination with biphenyl·thiamethoxam or highly effective cypermethrin for controlling red fire ants. The technical method of the present application significantly improves the control effect on red fire ants, can quickly control red fire ants, and when the same number of Steinernema riobrave (abbreviated as Sr) insect pathogenic nematodes are applied, the mortality rate of red fire ant workers in the treatment with the addition of a high dilution multiple of chemical agents is significantly higher than that in the treatment with nematodes alone. Compared with the single use of insect pathogenic nematodes, the limitation of poor short-term control effect on red fire ants is overcome. Compared with chemical control, there is no high dosage and environmental pollution problem, the amount of chemical agents used is greatly reduced, and it is more green and safe. Compared with the boiling water method, it is more convenient because there is no need to carry heating equipment.

Description

A method for controlling red imported fire ants by combining insect pathogenic nematodes with chemical pesticides

Technical Field

The present invention relates to the technical field of biological control and chemical control, and in particular to a method for controlling red imported fire ants by combining insect pathogenic nematodes with chemical pesticides, thereby enhancing the pathogenicity of the insect pathogenic nematodes to the red imported fire ants and reducing the use of chemical pesticides.

Background technique

The red fire ant ( Solenopsisinvicta Buren ) is a major and vicious invasive pest that causes serious damage to agriculture, forestry and animal husbandry, and also poses a threat to human life and safety. There are usually two main methods for its prevention and control: eradication and control. Eradication means completely eliminating the number of invasive pests through chemical means, regardless of the impact of invasive pests on the local ecology; while control means reducing the population of invasive pests through integrated prevention and control measures, thereby weakening their impact on the local ecology and slowing down their further spread. However, at present, both eradication and control mainly rely on the large-scale use of contact chemical pesticides such as cypermethrin and clothianidin for prevention and control. As the dilution multiple of chemical agents decreases, the mortality rate of red fire ants will increase, leading to the large-scale use of pesticides in the field. This not only causes serious pollution to the environment, but also causes great damage to the population of local ants, and even causes problems such as red fire ants developing resistance to pesticides. Therefore, one of the solutions is to reduce the use of chemical pesticides or combine them with other prevention and control measures.

Entomophilous nematodes are obligate parasites of insects. They have the advantages of actively searching for hosts, killing hosts with high efficiency, and having a wide range of hosts. Therefore, they are developed as new and efficient natural insecticides. Although entomopathogenic nematodes have a certain lethal effect on red fire ants, they are slow to take effect and have low insecticidal efficiency. In recent years, the use of entomopathogenic nematodes mixed with chemical pesticides has achieved good control effects in the management of various pests such as leek maggots, white moths, and cutworms. Chemical agents usually act quickly and can quickly reduce the activity and number of red fire ants, create more favorable conditions for the application of nematodes, and provide strong initial control. The nematodes then inhibit the recovery of the ant colony for a long time through their biological effects. However, there is currently no control and evaluation of the optimal ratio of entomopathogenic nematodes mixed with trace chemical pesticides for the control of red fire ants in China.

The current technologies for preventing and controlling red fire ants mainly include:

1. Boiling water treatment:

Boiling water treatment usually uses boiling water, and hot water at 70℃-80℃ can also be used. Each ant nest requires about 6 to 10 liters of water, which is slowly injected into the ant nest, and ensure that the water fully penetrates to cause the internal structure of the ant nest to collapse. High-temperature boiling water and hot water can effectively inactivate individuals in the ant nest. It is reported that the prevention and control effect of this method is between 20% and 60%. If the treatment is carried out continuously for 5 to 10 days, the effect may be more significant. Disadvantages: A large amount of boiling water is required, and the operation is also more complicated. When using it, it is necessary to avoid scalding surrounding plants and staff.

2. Chemical irrigating nests:

Chemical irrigating is a method of irrigating the nest of red fire ants with an aqueous solution of contact-killing agents. The high-concentration chemical aqueous solution penetrates the soil and directly spreads to the entire ant nest, causing the red fire ants to die after coming into contact with the active ingredients. These active ingredients are mainly chemical substances that are toxic to the nerves of red fire ants, which can inhibit the transmission of nerve signals of red fire ants, causing them to become paralyzed or overexcited and die. Disadvantages: high residue, which will pollute the environment; large dosage, low efficiency; and not suitable for large-scale application.

3. Insect pathogenic nematode aqueous solution:

Usually, control is carried out by sprinkling or injecting an aqueous solution of infested insect pathogenic nematodes. Use a shower or sprayer to sprinkle infested insect pathogenic nematodes on the ant nest and its surroundings, or use a syringe to inject the aqueous solution into the ant nest about 0.5 meters away from each mound. During the injection process, the syringe should inject the aqueous solution at a uniform speed and gradually remove it from the mound to ensure the uniform distribution of the nematodes. Disadvantages: Slow effect, insect pathogenic nematodes are easily affected by environmental factors, thus reducing their lethal effect; relying on the use of aqueous solutions, it is easy to cause the red fire ants to migrate or split nests, thereby reducing the control effect.

Summary of the invention

The object of the present invention is to provide a method for controlling red fire ants by combining insect pathogenic nematodes with chemical pesticides. The existing application of insect pathogenic nematodes to control red fire ants mainly uses an aqueous solution of insect pathogenic nematodes, which is slow to take effect and cannot act quickly on red fire ants, resulting in a decrease in the control effect. The technical method of the present application significantly improves the control effect of red fire ants, can quickly control red fire ants, and when the same number of Steinernemariobrave (abbreviated as Sr) insect pathogenic nematodes are applied, the treatment with a high dilution multiple of chemical agents has a significantly higher mortality rate for red fire ant workers than the treatment with nematodes alone. Compared with the single use of insect pathogenic nematodes, it overcomes the limitation of poor short-term control effect on red fire ants. Compared with chemical control, there is no high dosage and environmental pollution problems, the amount of chemical agents used is greatly reduced, and it is more green and safe. Compared with the boiling water method, it does not need to carry heating equipment, which is more convenient.

To achieve the above object, the present invention adopts the following technical solution:

A method for controlling red imported fire ants by combining insect pathogenic nematodes with chemical pesticides, wherein the insect pathogenic nematodes are used in combination with biphenyl·clothianidin or high-efficiency cypermethrin to control red imported fire ants.

Preferably, the ratio of the number of insect pathogenic nematodes to red fire ants is 400:1.

Preferably, the use concentration (total active ingredient concentration) of the bifenthrin·clothianidin suspension is 0.3125 μg/mL-2.5 μg/mL, wherein the mass ratio of bifenthrin to clothianidin is 1:1.

Preferably, the use concentration of the highly effective cypermethrin emulsion in water is 0.078125 μg/mL-0.625 μg/mL.

Preferably, the insect pathogenic nematode species is Steinernemario brave .

Preferably, the method specifically comprises the following steps: conducting the experiment in a plastic box with a diameter of 85 mm and a height of 85 mm and with a lid, laying two layers of filter paper with a diameter of 85 mm in each box; adding 1 mL of biphenyl·thiamethoxam or highly effective chlorpyrifos to each plastic box; and subsequently, adding infective insect pathogenic nematodes and red fire ant worker ants in a ratio of nematodes to red fire ants of 400:1.

The advantages of the present invention are:

1. The method of combining insect pathogenic nematodes with chemical pesticides has the advantages of reducing the use of chemical pesticides, reducing chemical pesticide residues and reducing the impact of pesticides on the environment.

2. Compared with physical control of red fire ants, the use of insect pathogenic nematodes combined with chemical pesticides has the advantages of simple use, easy portability and high insecticidal efficiency.

3. Compared with using chemical control alone, the use of insect pathogenic nematodes combined with chemical pesticides can enhance the pathogenicity of insect pathogenic nematodes and increase the mortality rate of red fire ants.

4. Compared with biological control, the use of insect pathogenic nematodes combined with chemical pesticides is more effective and can suppress the number of red fire ants in a shorter period of time.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows the corrected mortality rate of red imported fire ants compared to the number of insect pathogenic nematodes and red imported fire ants at different Sr infection stages;

Figure 2 shows the effects of three chemical pesticide dilutions on the survival rate of insect pathogenic nematodes during the Sr infection period;

Figure 3 shows the effects of chemical insecticides at different dilution multiples on the survival rate of red fire ants: A is highly effective cypermethrin, B is biphenyl·thiamethoxam, and C is avermectin;

Figure 4 shows the effects of the combined use of insect pathogenic nematodes and chemical pesticides on the survival rate of red fire ant workers during the Sr infection period: A highly effective chlorpyrifos, B biphenyl·thiamethoxam.

Detailed ways

In order to make the above features and advantages of the present invention more clearly understood, the following embodiments are given for detailed description. The methods of the present invention are all conventional methods in the art unless otherwise specified.

Example 1

A method for combining insect pathogenic nematodes with trace chemical agents, wherein the common contact chemical agents used are biphenyl clothianidin, highly effective cypermethrin and avermectin, and the scientific name of the insect pathogenic nematode species used is Steinernemariobrave , referred to as Sr, and comprises the following sequential steps:

1. Propagation of entomopathogenic nematodes during the infective stage

Place the wax moth larvae in soil containing infective entomopathogenic nematodes and allow the nematodes to infect the wax moth larvae for 6 to 8 days. During the infestation period, the wax moth larvae were manually de-coated every day and the wax moth larvae were obtained after they died. Four to five wax moth larvae were placed in a 6 cm petri dish with the opening facing upwards, which was lined with two pieces of filter paper with a diameter of 5 cm and kept moist with distilled water. The petri dish containing the wax moth larvae was floated in another 9 cm petri dish with the opening facing upwards, which was filled with 5 mL of distilled water. The entire system was placed in an incubator at 25 °C and waited for 7 to 8 days. During this period, the humidity of the filter paper in the 6 cm petri dish was observed every day. As the entomopathogenic nematodes develop in the larvae and transform into infective stages, the nematodes will leave the larvae and move along the filter paper and the 6 cm petri dish to the distilled water in the 9 cm petri dish. In this way, the aqueous solution of the infective insect pathogenic nematodes can be collected.

2. Determination of the toxicity of entomopathogenic nematodes to red imported fire ant workers during the infestation period

Two layers of filter paper with a diameter of 30 mm were placed in a plastic box with a lid (30 mm in diameter and 32 mm in height), and an appropriate amount of distilled water was added to keep it moist. Ten red fire ant workers of basically the same size were added to each box, and different concentration gradients of Sr-infected insect pathogenic nematodes were added using a pipette. The concentration gradients were 50:1, 100:1, 200:1, 400:1, and 800:1 for the ratio of nematodes to red fire ants. At the same time, an equal amount of sterile water (without nematodes) was set up as a control. Each of the above treatments was repeated 20 times and placed in an incubator at 26 °C and 70% relative humidity. The death of red fire ant workers was observed and recorded every 24 hours.

The results are shown in Figure 1. Under the treatment of different insect pathogenic nematode concentrations, the mortality rate of red fire ant workers showed a gradual upward trend with the increase of observation time. However, it is not the case that the more insect pathogenic nematodes there are, the more effective it is in causing the death of red fire ant workers. On the 7th day after the application of insect pathogenic nematodes, it was found that the best lethal effect was shown when the ratio of nematodes to red fire ants was 400:1, with a mortality rate of 25.26%. The next highest was 15.26% at 100:1, 9% at 800:1, 6.5% at 200:1, and 6% at 50:1.

3. Determination of resistance of insect pathogenic nematodes to chemical pesticides

In a 35 mm diameter petri dish, 4 mL of bifenthionidin suspension (the mass ratio of bifenthionin to clothianidin was 1:1) with a total active ingredient concentration of 250 μg/mL, 62.5 μg/mL of highly effective cypermethrin emulsion in water, and 22.5 μg/mL of avermectin dilution were added. 100 Sr-infected insect pathogenic nematodes were added to each petri dish using a pipette, and each treatment was repeated 20 times. The treatment without chemical pesticides was used as a blank control. The petri dish was placed at 26 °C and 70% relative humidity for 72 hours. The survival of the nematodes was observed under a microscope every 24 hours, and the survival rate was calculated.

The results are shown in Figure 2. The survival rates of Sr-infected entomopathogenic nematodes exposed to biphenyl·thiamethoxam, cypermethrin and avermectin were close to 100% at 24 hours, 48 hours and 72 hours, with no significant difference from the blank control group. This shows that Sr-infected entomopathogenic nematodes are not affected by the stimulation of these three chemical pesticides and can survive normally.

4. Determination of pathogenicity of different chemical pesticides to red imported fire ants

The experiment was conducted in a plastic box with a diameter of 85 mm and a height of 85 mm. Two layers of filter paper with a diameter of 85 mm were laid in each box. Thirty red imported fire ant workers of basically the same size were added to each box, and 1 mL of chemical pesticides of different concentrations were added using a pipette. Four concentration gradients were set for high-efficiency cypermethrin, biphenyl·thiamethoxam, and avermectin, and the dilution multiples were 8×10 ⁴ times, 1.6×10 ⁵ times, 3.2×10 ⁵ times, and 6.4×10 ⁵ times, respectively. The final concentrations of the active ingredients were as follows: 0.625, 0.3125, 0.15526, 0.078125 μg/mL of highly effective cypermethrin; 2.5, 1.25, 0.625, 0.3125 μg/mL of biphenyl·thiamethoxam; 0.225, 0.1125, 0.05526, 0.028125 μg/mL of avermectin. The treatment with equal amount of sterile water without adding chemical pesticides was used as blank control. The plastic box was placed at 26 °C and 70% relative humidity for testing. Each treatment was repeated 5 times, and the mortality was observed and recorded every 3 hours.

The results are shown in Figure 3: 24 hours after the insecticide treatment, the survival rate of red fire ants workers decreased significantly compared with the control group at different dilutions of biphenyl·thiamethoxam and high-efficiency cypermethrin. In the dilution range of 8×10 ⁴ to 6.4×10 ⁵ times of high-efficiency cypermethrin, the survival rate of red fire ants tended to increase with the increase of dilution. The lowest and highest survival rates occurred at dilutions of 8×10 ⁴ and 6.4×10 ⁵ times, which were 27.8% and 61.1%, respectively. In the treatment of biphenyl·thiamethoxam, the survival rate of red fire ants had no significant difference with the increase of dilution, ranging from 27.8% to 44.4%. However, compared with the control group, avermectin at different dilutions had no significant effect on the survival rate of red fire ants 24 hours after the insecticide treatment.

5. Determination of the pathogenicity of chemical pesticides and entomopathogenic nematodes against red imported fire ants

Under the same environmental conditions as the above experiment, 1 mL of biphenyl·thiamethoxam with a total active ingredient concentration of 2.5 μg/mL (diluted 8×10 ⁴ times) and 0.3125 μg/mL (diluted 6.4×10 ⁵ times), and 0.625 μg/mL (diluted 8×10 ⁴ times) and 0.3125 μg/mL (diluted 1.6×10 ⁵ times) of high-efficiency cypermethrin were added to each plastic box. Subsequently, Sr-infected insect pathogenic nematodes with a nematode to red fire ant ratio of 400:1 and 30 worker ants of basically the same size were added in sequence. At the same time, treatment groups with separate application of pesticides and nematodes were set up, and the same amount of sterile water was used as a control. Each treatment was repeated 5 times. The biphenyl·thiamethoxam treatment group was observed for a total of 12 hours, and the high-efficiency cypermethrin treatment group was observed for a total of 12 hours. The death of worker ants was checked and recorded every 3 hours.

The results are shown in Figure 4: 12 hours after treatment, there was no significant difference in the survival rate of red fire ants between the treatment with nematodes alone and the control group. The survival rates of worker ants were 63.3% and 86% when cypermethrin was diluted 8× ¹⁰⁴ and 1.6× ¹⁰⁵ times, respectively; and at the same dilution multiple of the insecticide, if 12,000 nematodes were added, the survival rates were 31.3% and 83.3%, respectively. In the treatment with cypermethrin diluted 8× ¹⁰⁴ times, the treatment with more nematodes can significantly reduce the survival rate of worker ants, that is, improve the efficiency of insecticide. However, when the dosage of insecticide was reduced to 1.6× ¹⁰⁵ times, the treatment with more nematodes failed to significantly improve the efficiency of insecticide. In addition, the survival rates of worker ants were 31.3% and 45.3% when biphenyl·thiamethoxam was diluted 8×10 ⁴ times and 6.4×10 ⁵ times, respectively; while at the same dilution multiple of the insecticide, if 12,000 nematodes were added, the survival rates were 18% and 29.3%, respectively. Under the same dose of insecticide treatment, adding more nematodes can significantly reduce the survival rate of worker ants. In addition, when biphenyl·thiamethoxam diluted 6.4×10 ⁵ times was mixed with nematodes, the survival rate of worker ants was lower than that of biphenyl·thiamethoxam diluted 8×10 ⁴ times alone, that is, the insecticide efficiency was higher.

The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims (6)

1. A method for preventing and controlling solenopsis invicta by combining entomopathogenic nematodes with chemical pesticides is characterized in that the entomopathogenic nematodes are used for preventing and controlling solenopsis invicta by combining with biphenyl clothianidin or high-efficiency cypermethrin.

2. The method of claim 1, wherein the ratio of entomopathogenic nematodes to solenopsis invicta is 400:1.

3. The method of claim 1, wherein the concentration of biphenyl clothianidin suspending agent is used in the range of 0.3125 μg/mL to 2.5 μg/mL.

4. The method of claim 1, wherein the lambda-cyhalothrin emulsion in water is used at a concentration of 0.078125 μg/mL to 0.625 μg/mL.

5. The method of claim 1, wherein the entomopathogenic nematode species is STEINERNEMA RIOBRAVE.

6. The method according to claim 1, characterized in that it comprises in particular the following steps: experiments were carried out in capped plastic boxes of diameter 85 mm and height 85 mm, two layers of filter paper of diameter 85 mm were laid in each box; each plastic box is respectively added with 1 mL of biphenyl clothianidin or high-efficiency cypermethrin; then, the entomopathogenic nematodes and the solenopsis invicta are sequentially added in the quantitative ratio of 400:1 in the infection period.