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Cotton bollworm, belonging to the genus Botanidae of the lepidoptera family Noctuidae, is an omnivorous pest. Cotton bollworm is distributed throughout China, in the north of China occurs more seriously, in addition to harming cotton, its host plants are corn, wheat, peanuts, sorghum, bell peppers, tobacco, potatoes, tomatoes, chickpeas, flax, etc., but also to harm some fruit trees, vegetables, etc., especially like to eat cotton and corn reproductive organs.
With the reform of the tillage system and the vast majority of spring maize being changed to summer maize, cotton bollworm has become one of the main pests of the maize ear stage in the Huang-Huai-Hai, seriously harming the female ears and grains of summer maize, and in some years even exceeding the corn borer.
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1. Agricultural control
(1) Clean pastoral, autumn ploughing and winter irrigation, suppress the base number of overwintering pupae Cotton bollworms overwinter in the soil with old mature larvae after autumn, mostly 2.5 to 6cm under the surface, the deepest up to 9cm, corn should be turned deeply after harvesting, can destroy the hiding environment of overwintering pupae, a large number of frozen and killing overwintering pupae, effectively suppress the source base of insects in the coming year. Winter ploughing can destroy the pupal chamber, and part of the insect pupae into the deep soil layer or soil surface, the deep soil layer pupa is difficult to feather, and the pupa on the soil surface is easy to be eaten by birds and animals or freeze to death, if you can irrigate water after winter ploughing, the soil moisture increases, and the mortality rate of pupae can be improved.
(2) Rational adjustment of crop layout, improve corn planting methods Cotton bollworms are heterogeneous, host plants are many, and reasonable adjustment of crop layout and variety collocation can reduce the harm of cotton bollworms. For example, planting enticing crops such as alfalfa, chickpeas, onions and carrots around the cornfield can induce a large number of adult cotton bollworms during the full flowering period, which can be gathered and annihilated. Reasonable seed rotation and increased field biodiversity can effectively reduce the pest of cotton bollworm.
(3) Strengthen field management and promote mulch film cultivation The main maize planting models in China are tiankan (ground edge) corn, dryland (open ground) corn and mulch film corn. The promotion of mulched corn has promoted the growth of corn and its ability to resist diseases and insects. The method of filigree cutting can also be adopted, that is, when the cotton bollworm larvae in the corn field have not drilled into the female ear of corn before the third instar, the control effect of manual cutting of the female ear filament is better.
2. Biological control
Using the parasitic or predatory natural enemies of cotton bollworms, fungi include white zombies, green zombies, bacteria such as Bacillus thuringiensis, parasitic natural enemies such as egg parasitic bees borer yellow red-eyed bees, corn borer red-eyed bees, etc., and larval parasitic wasps in the red lateral groove cocoon bees, cotton bollworm tooth lip bees, etc., predatory natural enemies such as Chinese grassflies, heterochromatic ladybirds, tortoiseshell ladybirds, grass black spiders, wasps and praying mantises, etc., all have a controlling effect on cotton bollworms.
3. Physical control
Adult cotton bollworms have the characteristics of phototropism and chemotacticism, and like to move, feed and lay eggs on flowering honey source crops, which can be lured and killed in a concentrated manner. According to the principle and method of booby-trap, it can be divided into light booby trap (mainly using 450W high-pressure mercury lamp and double-wave lamp lure), which can effectively reduce the adult bollworm and its spawning number during the feathering stage.
4. Chemical control
The best period for prevention and treatment is before the third age, and the following methods can be mainly used:
(1) Spraying leaves before three instars. It can spray chemical pesticides such as 2.5% high-efficiency cypermethrin emulsion 2000 times liquid, 4.5% high-efficiency cypermethrin emulsion 1500 times liquid.
(2) In late June, insecticidal granules are sprinkled in the corn heart leaves. Optional 0.1% or 0.15% cypermethrin granules 1.5g 14% chlorpyrifos granules or 3% butyric Budweiser granules each plant 1 to 2g, 3% octyl thiophos granules 2g per plant, 50% octyl thiophos emulsion according to 1100 mixed into the horn mouth, 2g per plant.
(3) Coating with seed coating agent containing insecticide ingredients. After coating, maize seeds have obvious effects on the growth rate and insect resistance of seedlings and adult plants.
(4) After the filament wilts, the insecticide is used to remove the insect at the filament drops. With 2.5% cypermethrin emulsion or 80% dichlorvos emulsion 200 to 400 times droplets at the top of the female panicle filament, each spike drops of the good liquid 0.5mL, 3d after the prevention effect can reach more than 90%, and can reduce the killing of natural enemies.
Source: Crop Diseases and Pests in China
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