Pieris caerulea is a larva of Pieris rapae. It occurs everywhere, and it mainly eats cabbage leaves. It is the main pest of Chinese cabbage. September-October is the season of high incidence of cabbage caterpillars, and farmers are expected to pay close attention to prevention and treatment.
First, the harm symptoms
The 1-2 instar larvae feed on the leaves of Chinese cabbage and leave a thin and transparent epidermis. The food intake of larvae older than 3 years of age is significantly increased. The leaves can be eaten into holes or nicks, affecting the normal growth of Chinese cabbage and its core. In severe cases, all the leaves were eaten, leaving only the veins and petioles, resulting in an outbreak. If the larvae are packed into the leaf ball, the larvae feed on the leaf ball, and at the same time excrete fecal contamination of the cabbage, resulting in a reduction in the commercial value of the cabbage. The wound can also easily lead to the occurrence of Chinese cabbage soft rot.
Second, prevention and control measures
1. Clean the pastoral. After the harvest, the stubble should be cleared in time and the soil should be deeply turned to eliminate a large number of insect sources.
2. Trapping adult worms. Using the phototaxis of Pieris rapae, black light was placed in the adult stage to trap and kill, in order to reduce the number of eggs laid.
3. Manual capture. For old larvae, careful killing can be captured in the early morning.
4. Scientific medication. The period of chemical control should be controlled before the hatching of egg until the third instar, when the drug resistance is very weak, timely medication is very important. Available with 2.5% deltamethrin emulsifiable concentrate 3000 times, 90% trichlorfon crystal 1000 times, 50% killer pine extract, BT emulsifiable oil or insecticide 500-800 times, 21% kill emulsifiable concentrate 4000 times Liquid, 2.5% deltamethrin emulsifiable concentrate 3000 times solution, 2.5% kungfu emulsifiable concentrate 5000 times solution, 25% (or 30%) diflubenzuron 1 (or 3) 500-1000 times solution, sprayed every 7 days 1 time, spray 2-3 times continuously. Pay attention to timely control, alternating medication.
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