In recent years, with the increasing use of wheat harvesting techniques, a variety of ground coverings such as wheat stubble, straw, and remnants often remain in summer corn fields. These materials create favorable conditions for the proliferation of various pests, which can lead to severe infestations. Pest damage not only results in the loss of corn leaves but also facilitates the spread of viruses, potentially causing disease outbreaks. In extreme cases, it may even lead to stunted growth or plant death. Therefore, effective pest control is essential during the summer sowing of maize.
**Pest Control**
The main seedling pests affecting summer-sown maize include thrips, aphids, wheat midges, cutworms, planthoppers, spider mites, armyworms, bollworms, and wireworms. For ground pests like wireworms, applying 1000 ml of irrigation agent or phoxim per acre during watering can be effective. For pests such as thrips, moths, wheat midges, corn borers, bollworms, armyworms, and aphids, a mixture of 20g of 10% imidacloprid wettable powder or 30ml of bifenthrin in 30-40kg of water per acre can be used for spraying. When spider mite infestation reaches 5%, it is recommended to spray with 15% abamectin emulsion diluted 1500-2000 times or 20% acephate emulsion diluted 2000 times.
**Disease Prevention**
The primary diseases affecting young summer corn plants include bacterial wilt, rough dwarf disease, and maize dwarf mosaic virus.
**Bacterial Wilt**: This disease is more common in continuous corn fields with high humidity and sudden rainfall. Early symptoms include gray-green leaves that gradually wilt and turn yellow. The roots and base of the stem become water-soaked, then brown and rotten. To manage this, a combination of Rhizoctonia and Tianfengsu should be sprayed at noon on sunny days, followed by another application every 3–5 days.
**Rough Dwarf Disease**: Caused mainly by the feeding of Laodelphax striatellus (brown planthopper), this disease leads to white waxy protrusions on the back of leaves when the corn has 4–5 leaves. The leaves become stiff, thick, and dark green, while the upper internodes shorten and the top leaves cluster together. Infected plants should be removed, and control of the planthopper is crucial. Before and after corn emergence, spraying with 50% carbendazim diluted 800 times for 1–2 times can help prevent the disease.
**Maize Dwarf Mosaic Disease**: Spread mainly through aphids or mechanical wounds, this disease causes green spots between the veins at the base of the leaf, which later develop into dotted lines along the veins. The leaf veins lose color and turn yellow, while the areas on either side of the veins remain green, forming distinct green stripes. To manage this, focus on controlling aphids, remove infected plants, and spray a mix of foliar nutrients and disease control agents. A solution of 1:1:2000 omethoate and dichlorvos can also be applied, especially during the 3-leaf and 5-leaf stages, offering better control outcomes.
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