(1) Plutella xylostella
Plutella xylostella mainly harms cabbage and cabbage vegetables, mostly young larvae concentrate on the heart leaves, only feeding on mesophyll, leaving the epidermis. The 3 ~ 4-year-old larvae can eat the leaves into holes or nicks, and in severe cases, the leaves are eaten into a net shape, leaving only veins. Plutella xylostella can produce11~13 generations a year, and the peak occurs in August ~1October in autumn.
Control methods: First, combined with seedbed production and seedling management, timely remove dead branches and rotten leaves, remove egg pieces and newly hatched larvae. Secondly, during the peak period of 2nd instar larvae, the commonly used pesticides are 5% Regent 3000 times solution, 1% insecticide 3000 times solution, 5% chlorfluazuron 1500 times solution +80% dichlorvos 1000 times solution spray, among which chlorfluazuron should be controlled at the peak period of egg incubation.
(2) Twill night
Spodoptera litura mainly damages cabbage and cabbage, not only at the seedling stage, but also at the adult stage. Newly hatched larvae gather to eat mesophyll, and after the 2nd instar, they are scattered and can eat the leaves into a broom shape (leaving only the epidermis). The 3rd instar larvae eat the leaves into nicks or holes, and the 4th instar larvae enter the gluttony stage.
Spodoptera litura is a warm-loving pest, and its damage is most serious in July ~10 in a year. The control methods are as follows: first, combining seedbed production and seedling management, timely remove dead branches and rotten leaves, remove egg pieces and newly hatched larvae. Secondly, the larvae can be treated before the 3rd instar, and after the 4th instar, the pesticides should be sprayed around the evening. The commonly used pesticides are 1% insecticide 3000 times solution, 48% chlorphenamine 1000 times solution, and 5% carboxim EC1000 ~10. When young and old larvae are mixed, they can be sprayed with 20% semi-full colloidal suspension 1500 times solution or 5% Regent colloidal suspension with 4000 times solution.
(3) Spodoptera exigua
It mainly harms cabbage, cabbage and lettuce, celery and other vegetable seedlings. The newly hatched larvae gather, feed on the back of the leaves, and draw a net to bite the mesophyll, leaving only the epidermis with transparent holes, which will disperse after being a little bigger. After the third instar, the leaves can be eaten into holes or nicks, and in severe cases, the leaves can be eaten up, leaving only veins and petioles, so that the seedlings die. The 4th instar larvae lie in the daytime and come out at night, which has suspended animation.
Spodoptera exigua generally occurs in the middle and lower reaches of the Yangtze River for 4-6 generations, and its eggs are mostly laid on the back of leaves and covered with white loose fluff. High temperature is conducive to the occurrence. If high temperature comes early, lasts for a long time, and the rainfall is less, it may occur in a big way. Usually, the damage is more serious from August to September.
The methods to control Spodoptera exigua are as follows: firstly, combined with seedbed production and seedling management, dead branches and rotten leaves are removed in time, and egg pieces and newly hatched larvae are removed. Second, chemical control, commonly used chemicals are 10% anlubao EC 1000 ~1500 times, 5% chlorhexidine EC1000 ~1500 times, and 5% chlorhexidine EC/kloc.
(4) vegetable borer
It mainly harms the seedlings of cabbage, Chinese cabbage and mustard, and it is a borer, which harms the heart leaves and leaves at the seedling stage. The damaged seedlings stop growing or wilt and die because of the destruction of their growing points.
The cabbage moth likes high temperature and low humidity environment, and the damage peak is August ~10. The main control methods are as follows: first, when making seedbeds, dig deeply to clean the fields and reduce the source of insects. Second, proper irrigation can increase the humidity of seedbed and inhibit the growth of pests. Third, chemical control, commonly used chemicals are 4,000 times of 2.5% Kung Fu EC and 3,000 times of 20% Miesaoli EC.
(5) Yellow-curved flea beetle
The yellow striped flea beetle mainly harms cabbage vegetables, cabbage and so on. Adults can bite cotyledons and true leaves into many small holes, and in severe cases, the whole seedling dies. Larvae only harm roots, eat root bark, bite off fibrous roots, and make plants wilt and die.
The striped flea beetle has 4-6 generations a year and overwinters as an adult. Adults have phototaxis, like temperature but resistant to low temperature, and generally occur seriously in autumn. The field with high humidity is more serious than the field with low humidity.
Prevention and control methods: First, when the seedbed is made, deep ploughing is carried out to clean the field and reduce the source of insects. Secondly, chemical control can be carried out by spraying 48% chlorpheniramine 1000 times, 52.25% agropyron 1000 ~1200 times and 50% phoxim1000 times.
(6) snails
Snails can harm almost all vegetable seedlings. They can bite stems, leaves and growing points. Snails are mollusks, which often live in farmland, weeds or rocky piles, and often crawl out after rain to harm vegetables, and breed1~ 2 times a year. Snails like damp, and in case of rainy days, they do harm by day and night activities; When it is dry, it lurks during the day and moves at night.
The methods to prevent and control snails are as follows: first, when making seedbeds, clean the fields, eliminate weeds in the fields and ditches, and reduce the breeding grounds of snails. Second, sprinkle some quicklime around the seedbed. Thirdly, around the seedbed, even in the seedbed, apply Mida at regular intervals, with10 ~ 20 grains per pile.