Pyrethroid pesticides are the third largest insecticide after organophosphate and carbamate, and they play an important role in the global market. Pyrethroid insecticides can not only control a variety of pests such as Lepidoptera, Coleoptera, Hemiptera and Homoptera, but also often act as "firefighters" to control underground pests.
Using pyrethroid pesticides to control underground pests has good contact and stomach poisoning effects. It also has the characteristics of fast insecticide speed, thorough insecticide, wide insecticide spectrum, low cost and low residue. At the same time, it also has certain attracting characteristics for underground pests. The more common ones are fenvalerate, cypermethrin ester, beta cypermethrin, bifenthrin, cyhalothrin and Cyfluthrin. Although pyrethroid pesticides have the disadvantage of short duration in controlling underground pests, their advantages are also outstanding, that is, low cost, small residue and fast effect.
To solve this problem, farmers have two ways to deal with it:
One is to use pyrethroid pesticides as "firefighters". That is, when underground pests are rampant, use the rapid effect of pyrethroid pesticides to quickly reduce the number of underground pests and minimize economic losses.
The second is to mix with long-acting and systemic insecticides such as phoxim, chlorpyrifos, and clothianidin. This not only ensures the effective killing of existing underground pests, but also enhances the lasting preventive effect on underground pests. The more common ones on the market are phoxim + cypermethrin, chlorpyrifos + cypermethrin, bifenthrin + clothianidin, cyfluthrin + clothianidin, beta cypermethrin + clothianidin, etc.
Not all pyrethrins are suitable for underground pest control
It is well known that underground pests are more sensitive to pyrethrin pesticides. For example, when controlling cutworms, low-cost pyrethrin insecticides are usually used. However, as cutworms become more resistant to pyrethrin insecticides, traditional pyrethrin pesticides no longer have control advantages, such as fenvalerate, cypermethrin, beta cypermethrin, etc. The emergence of lambda-cyhalothrin and cyfluthrin has made up for the resistance shortcomings of pyrethrin insecticides in controlling underground pests.
Whether it is cyhalothrin or cyfluthrin, fluorine atoms are introduced into pyrethrin molecules, which greatly enhances the activity of the compounds, thereby achieving the purpose of improving insecticidal and acaricidal activity. Although these two pyrethrins have good control effects on underground pests, practical data show that cyfluthrin's control efficiency and half-life in soil are higher than cyhalothrin.
Bifenthrin is the fourth largest pyrethroid insecticide after beta cypermethrin, lambda-cyhalothrin and cypermethrin. Compared with the above three pyrethroid insecticides, bifenthrin has better insecticidal and acaricidal abilities, which is its specialty; under the contact and stomach poisoning effects, it also has repellent and antifeedant effects, and also has a certain egg-killing ability, and has a good control effect on chewing pests and piercing-sucking pests.
However, among many pyrethroid insecticides, bifenthrin is indeed more distinctive, especially in wheat-growing areas, where bifenthrin is still the mainstream insecticide for controlling wheat spiders and wheat red spiders. The reason for this is that in addition to the insecticidal and acaricidal functions of bifenthrin, it is also related to the fact that bifenthrin can play a relatively excellent effect in low temperature periods.
Bifenthrin has the characteristics of poor mobility in the soil and a long half-life. It is suitable for long-term control of underground pests. When mixed with nicotinoid insecticides with strong systemicity, such as thiamethoxam, clothianidin, and dinotefuran, it can not only make up for the defects of nicotinoid insecticides that are good at repelling but weak in killing insects, but also increase the systemic conduction capacity of the mixed agent, so as to achieve the effect of killing underground pests and preventing piercing-sucking pests during the growth period of crops. Especially for the more stubborn leek maggots, garlic maggots, and onion maggots, at the recommended amount, it can also achieve a relatively ideal control effect, thus solving the dependence of leek, garlic, and onion on highly toxic and high-residue pesticides.
It can be seen that targeting underground pest control is another important direction for realizing the value of pyrethroid products.
Comprehensive evaluation
The pyrethroid pesticides that are widely used in the market are mainly lambda-cyhalothrin, cyfluthrin, bifenthrin, and deltamethyrin. Among these types of pyrethroid pesticides, except for deltamethyrin, which is ineffective against mites, the others have a certain degree of control effect against mites, and bifenthrin has a higher control effect against mites.
Cyfluthrin has the best control effect against underground pests, followed by lambda-cyhalothrin; deltamethyrin has the highest insect toxicity among pyrethroid pesticides, so its control effect is better and the knockdown speed is fast, but deltamethyrin is easily decomposed by ultraviolet rays and has a short duration of effect.
Lambda-cyhalothrin is a large variety among pyrethroid pesticides, with high efficiency and low toxicity, and it kills both insects and mites and has a wide insecticide spectrum. Lambda-cyhalothrin is highly irritating to human skin. If it is not properly protected during use, it is very easy to cause skin itching. Now this problem has been gradually solved through microcapsule technology.
