In recent years, due to shifting climatic conditions, grasshoppers have transitioned from being a secondary pest in summer soybean fields to the primary threat. Newly hatched larvae feed on young leaves, leaving behind a thin epidermis. By the third instar, their feeding intensity increases significantly, causing leaves to be eaten with visible notches, often leaving only the veins. On average, infestations can reduce annual soybean yields by 10% to 15%, while severe outbreaks may lead to losses of up to 20% to 30%, posing a serious risk to soybean production.
Grasshoppers typically complete one or two generations per year. Mature larvae reside in silken soil and overwinter. The overwintering larvae emerge between April and May. The first generation mainly affects rapeseed, while the second generation targets soybeans in late August and early September. Adult grasshoppers are highly attracted to various light sources, especially black lights, and tend to gather in clusters. They lay eggs in plants such as Liko, Asteraceae, and Solanaceae. The fourth and fifth instars consume the majority of the larval food intake, accounting for over 80% of total consumption.
**Agricultural Control:**
During the grasshopper spawning season, before eggs hatch, it is essential to remove weeds from fields and the surrounding ground. Collected grass should be buried to prevent further spread. In infested years, larvae should be prevented from entering bean fields by digging and removing them manually.
**Chemical Control:**
1. **Fumigation:** During the adult stage in August, mix 100–150g of 80% dichlorvos with 4kg of sawdust and wheat bran, making 40 piles per acre. Place these under soybean plants, which can maintain effectiveness for 8–10 days.
2. **Spraying:** Seven to ten days after adult emergence, when larvae are in the early instar stage, is the best time for treatment. From late August to early September, apply:
- 25–35ml of 50% eucalyptus oil per acre;
- 20–30ml of 2.5% emulsifiable concentrate per acre;
- 20–30ml of 20% emulsifiable concentrate per acre.
Dilute with 50kg of water and spray evenly.
3. **Dusting:** Apply 2.5% trichlorfon powder, 3% mixed Granville powder, or 2% acaricidal pine powder at a rate of 1.5–2kg per mu.
**Physical Control:**
Install black light traps in soybean fields to capture adult grasshoppers effectively. This method helps reduce population levels and provides an eco-friendly approach to pest management.
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