10% Cypermethrin Emulsifiable Concentrate, registered for cabbage caterpillar on vegetables, 20-30 mL/mu, spray.
The product performance statement summarizes in one sentence the three modes of action of pyrethroids:
It possessesContact action, stomach toxicity, and a certain fumigant effect.and has a relatively long residual efficacy.
The superposition of these three modes of action is the reason for the rapid knockdown effect of this type of pesticide.
1. How do the three modes of action occur respectively?
Contact actionThe insecticide solution contacts the insect body and penetrates the cuticle to enter the body. This is the primary route of action for pyrethroids — when sprayed, the solution directly hits the insect, causing excitation, convulsions, and paralysis within seconds to minutes.
Stomach poisonPests feeding on treated leaves absorb the insecticide through the digestive tract. For cabbage caterpillars that chew on leaves, stomach toxicity is important.
FumigationThe chemical volatilizes into gas and enters the insect body through spiracles. The fumigant action of pyrethroids is limited, but it can be enhanced in enclosed spaces such as greenhouses.
The combination of the three = fast knockdown + broad coverage.This is why pyrethroids are referred to as "fast-acting insecticides."
II. Mechanism of Action: Sodium Channels
The target site of action of pyrethroid insecticides isSodium channels of the nerve axon请提供需要翻译的中文段落。
Under normal conditions, sodium channels open briefly during nerve impulse conduction and then close. Pyrethroid insecticides cause sodium channelsContinuous opening, the nerves remain continuously excited, ultimately leading to paralysis and death.
This is completely different from organophosphates (acetylcholinesterase) and neonicotinoids (acetylcholine receptors).The three mechanisms do not interfere with each other, which is the basis for rotation.
III. Key points for the control of cabbage caterpillars
The cabbage caterpillar (larva of the small white butterfly) is a major pest of cruciferous vegetables.
Mode of damageThe larvae feed on the leaves, causing holes and notches. In severe cases, only the leaf veins remain.
Occurrence patternMore than one generation per year (3–4 generations in the north, 7–8 generations in the south), with overlapping generations. Two peaks occur in spring and autumn.
Key control measures请提供需要翻译的中文段落。Early larval stageBefore the third instar, the larvae have thin body walls, weak pesticide resistance, and a small feeding capacity. After the third instar, their food consumption increases substantially and pesticide resistance rises.
Determination methodExamine the size of the holes on the leaves. Small holes (1–2 mm) indicate that the larvae are still small; large holes indicate that they have already grown larger.
IV. 20-30 mL/mu
The 10% content is relatively low.(Compared with 4.5% beta-cypermethrin, although the content is higher, the active entity is different), 20–30 mL/mu is equivalent to 2–3 g of active ingredient per mu.
The dosage range corresponds to larval instar and population density: use the lower limit for young larvae, and the upper limit for older larvae or high population density.
V. 5-day interval, 3 times per season
The pre-harvest interval for vegetables is 5 days, with a maximum of 3 applications per season.
Five days is relatively friendly to leafy vegetables (leafy vegetables grow quickly and are harvested frequently). But3 applications maximumThis means it must be rotated with other mechanisms.
6. Toxic to bees, fish, and silkworms.
Precautions:
This product is toxic to bees, fish and other aquatic organisms, and silkworms. During application, avoid effects on surrounding bee colonies.Do not use near flowering plants during the flowering period, silkworm rearing rooms, or mulberry fields.Keep away from aquaculture areas when applying the pesticide. Do not clean application equipment in rivers, ponds, or other water bodies.
Pyrethroids are highly toxic to bees, highly toxic to fish, and highly toxic to silkworms.— These three are common risks shared by all pyrethroids.
Why is it so toxic to aquatic organisms?Pyrethroids are highly lipophilic and readily penetrate fish gills to enter the body, while fish have a weak capacity to metabolize such compounds. Extremely low concentrations (at the ppb level) can be lethal.
Practical constraints请提供需要翻译的中文段落。
Ditches and ponds around vegetable fields should be avoided.
No application during the flowering period (including surrounding nectar source plants).
- Prohibited around sericulture areas
7. Resistance: Pyrethroids are an older class with established resistance issues.
Pyrethroids have a long history of use in China.The resistance of Pieris rapae, Plutella xylostella, and Helicoverpa armigera to pyrethroids is generally severe.请提供需要翻译的中文段落。
In some regions, the resistance ratio of diamondback moth (Plutella xylostella) to pyrethroids has reached several hundredfold, rendering these insecticides virtually ineffective.
Why is this?请提供需要翻译的中文段落。
Pyrethroids should not be used as a sole control measure.
Must rotate with agents of different mechanisms of action.
In areas with severe resistance, priority should be given to pesticides with novel modes of action.
Alternate the direction of rotation.请提供需要翻译的中文段落。
- Diamide insecticides (chlorantraniliprole, cyantraniliprole)
- Microbial sources (Bacillus thuringiensis Bt, spinosad, abamectin)
- Insect growth regulators (chlorfluazuron, tebufenozide)
VIII. Precautions for Using Emulsifiable Concentrates
Do not mix with alkaline pesticides.(Pyrethroids decompose under alkaline conditions).
Secondary dilutionEmulsifiable concentrate should be diluted first before topping up with water to the required volume.
Wear protective equipment.Avoid skin contact.
Avoid applying pesticides during high-temperature periods.(Pyrethroids volatilize rapidly at high temperatures, have a short residual efficacy, and are unfriendly to applicators.)
9. Do not mix with alkaline pesticides.
Precaution 2: "This product must not be mixed with alkaline pesticides or other alkaline substances."
Pyrethroids will hydrolyze and lose efficacy under alkaline conditions. Common alkaline agents:
Bordeaux mixture
Lime sulfur mixture
- Copper hydroxide (some formulations are alkaline)
When preparing the pesticide solution, attention should also be paid to the pH of the water.Extremely hard water and alkaline well water may affect pesticide efficacy.
10. Integrated Management of the Cabbage Caterpillar (Pieris rapae)
Relying solely on chemical agents makes sustainable control difficult.Integrated strategy请提供需要翻译的中文段落。
Agricultural measuresClean up the field after harvest by removing crop residues and plowing, practice crop rotation, and avoid continuous cropping of cruciferous crops.
Physical measuresInsect-proof netting (to prevent adult oviposition); manual collection of larvae (for small areas).
Biological control请提供需要翻译的中文段落。
Here is the English translation: Please provide the Chinese paragraph you would like me to translate into professional and fluent English. I will return only the English translation as requested.Bacillus thuringiensis (Bt)Highly effective against cabbage caterpillars, with strong target specificity and no harm to natural enemies.
- Release of parasitic wasps (Cotesia glomerata)
- Protect natural enemies (ground beetles, spiders)
Chemical control.: Early instar larval stage, multi-mechanism rotation.
The advantages of Bt are worth emphasizing.It is effective only against lepidopteran larvae and is safe to bees, natural enemies, humans, and livestock, making it the most environmentally friendly option for controlling imported cabbageworm. Its disadvantages include slow action (taking 2–3 days to show efficacy) and short residual activity.