After entering the year of July each year, the occurrence of pests in the open-air and sheds is most serious. Nocturnal insect pests have a wide range of damages, from wheat and corn to cotton, beans, and various vegetable crops. Nocturnal larvae have large body sizes and most of them have gluttonous habits. Many vegetable leaves can be eaten overnight, leaving only light stalks. Now it will enter the season of the outbreak of pests of the moth, reminding farmers to carry out comprehensive prevention and control according to the characteristics of pest occurrence.
At present, the most serious insect pests in the northern region are mainly Spodoptera litura, Spodoptera exigua, and Brassica napus, especially Spodoptera litura, which has occurred in Shandong in recent years. Many vegetable farmers are incapable of doing anything about it. Describe the pest habits and comprehensive prevention and control measures.
1. Spodoptera litura. In the Shandong region, five generations can occur each year, and peaks occur in August and September of each year. Adults have the habit of nocturnal emission, 8 to 12 o'clock in the evening for the peak of adult activity, and have the characteristics of cluster takeoff, with strong phototaxis. When adults lay eggs, most of the eggs are produced on the back of the middle leaves of the plants. The tall, dense and dense green plants have more eggs. Newly hatched larvae gather near the egg mass to feed on the leaves, stems, flowers and fruits. After the 2nd age, it began to disperse, and it could be eaten on the day and night before 3rd instar. It only eated the leaves and left the epidermis and veins. It showed a white yarn hole shape, and it turned yellow afterwards. It was easy to identify. After 4 years of age, it enters a period of gluttony and has a feign death. Once disturbed, it falls to the ground. The mature larvae bore into the rhizosphere of the plant during the day and feed it at night. However, during the rainy days, they climb out and feed. Spodoptera litura prefers warm and humid climate conditions, and autumn rain is conducive to the outbreak of Spodoptera litura.
2. Spodoptera exigua. It is widely distributed, and its diet is also more complex. The living habits of adults and larvae are similar to that of Spodoptera litura. The difference is that the activity of Spodoptera exigua adults is from 8 to 10 o'clock in the evening; and the newly hatched larvae have tortoises. Habits, when food resources are in short supply, larvae can kill each other and can do long-distance migration, and transfer the host to continue to harm. After the larvae enter the final age, the overeating is even more pronounced, accounting for about 90% of the total amount of larvae. Beet armyworm harms more than 30 kinds of vegetables such as tomatoes and green peppers in addition to harming cruciferous vegetables. The most common occurrence in the summer room is Spodoptera exigua.
3. Brassica napus. In the Shandong region, 2-3 generations can occur in one year, and the damage is most serious from late August to early October. The emergence of Brassica culmorum is mainly affected by climatic conditions. Warm and moist are conducive to outbreaks. Therefore, cabbage witch moth in open-air vegetables will have a peak on autumn cabbage, cabbage and other vegetables. Adult females can produce up to 800 eggs. Eggs are usually produced on the back of the leaves. They have a single layer of about 100 grains per piece. The larvae habits are similar to Spodoptera litura.
Understand the habits of various pests, and recommend that farmers adopt comprehensive measures for prevention and control:
First, catch the active period of adult activity and focus on eliminating adults. In the occurrence period of the moth pests, adults can be trapped and killed by the black light in the field, especially for adults with cluster takeoff characteristics such as Spodoptera litura. In addition, sweet and sour vinegar pots can be placed in the field, placing 6-10 pots per acre (sugar and vinegar ratio of sugar: wine: vinegar: water = 6:1:3:10, and the need to add appropriate amount of trichlorfon). By killing adults, the amount of eggs in the field can be effectively reduced and the occurrence of pests can be reduced.
Second, manually remove the egg mass and destroy the larvae before dispersing. The nocturnal insect pests are more concentrated in spawning and can form larger egg masses. Therefore, in the adult spawning period, the vegetable farmer can manually remove the egg masses in the field and destroy them collectively. In addition, the newly hatched larvae of a variety of noctuid larvae have the property of agglomeration and use of artificial measures to control larvae during this period of time has a good effect. For mature larvae with stronger drug resistance, individual capture methods can also be used for prevention and control.
Again, biological control measures. In recent years, biological preparations of Beauveria bassiana and Bt emulsion have been used to control nocturnal moth pests and have achieved good results. For conditional lots, Trichogramma, etc. can also be used to control and release about 30,000 heads per acre.
Finally, chemical control measures are used. The critical period of chemical control of larvae of larvae is before 3rd instar, and can be controlled by 25% diafenthiuron 1500 times, 20% diflubenzuron No. 1 1000 times solution or 15% Avi chlorpyrifos 1500 times solution, etc. Benzoamide 600-800 times solution. When spraying, pay attention to alternate use of multiple agents to delay drug resistance. For larvae after 3rd age, pay attention to spraying time during the prevention and treatment, try to choose to do it in the early morning or early evening.
In addition, because the above-mentioned nocturnal moth pests are all wintering in the soil, for open-air plots, deep plowing and winter plowing after autumn harvest are very effective in killing overwintering pupae and reducing the number of insect populations in the next year.
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