Corn rough dwarf disease is primarily transmitted by the small brown planthopper (Laodelphax striatellus) in a persistent manner. In corn-growing regions with limited rice fields, when wheat is harvested, these planthoppers migrate into cornfields and surrounding grassy weeds, causing damage and overpopulation. This period coincides with the sensitive growth stage of summer maize, making it highly susceptible to the disease. The first generation of planthoppers poses the greatest threat to corn crops. After the harvest of corn and late rice, they move to grasses and weeds. When autumn wheat emerges, they transfer to wheat fields, where they continue to feed and overwinter, completing the annual disease cycle.
The symptoms of maize rough dwarf disease are characterized by stunted growth, with affected plants reaching only half to two-thirds the height of healthy ones. Infected plants can still develop, but their yield and quality are significantly reduced. The disease is entirely caused by the transmission of the virus through infected planthoppers. Therefore, controlling or eliminating the spread of the small brown planthopper is crucial in preventing the occurrence of this devastating disease. The following measures can be implemented for effective control.
First, field weeding is essential. The virus often survives in wheat, grassy weeds, and ditches. To prevent the spread of the disease, it's important to manage wheat bush dwarf disease and remove weeds from fields, slopes, and ditches. Reducing the population of Syrphidae crickets is also necessary. A recommended method is to apply 25% purofuran at a rate of 50 g per mu after the wheat turns green, or spray 50% monocrotophos diluted 5000 times. Weeds around the wheat field should also be treated. If needed, 20% glyphosate or 45% Roundup can be used at 550 ml per mu mixed with 30 kg of water, sprayed along the field edges to eliminate weeds and destroy the planthopper’s habitat.
Second, controlling planthoppers in wheat fields helps reduce the risk of virus transmission. Winter irrigation and the removal of overwintering nymphs of S. sibiricus are effective strategies. Herbicides like Dupond Superstars can be used to manage weeds in wheat fields. During early spring, joint control of wheat joints can help prevent overwintering adults from surviving. After wheat heading, integrated pest and disease management practices can further suppress the emergence of Laodelphax striatellus.
Third, adjusting the planting date of corn can help avoid the peak migration of planthoppers. Summer corn should be planted between late May and early June, ideally seven days before wheat harvest. Early planting in April can also help avoid the peak of overwintering adults, reducing the risk of infection.
Fourth, proper field management is critical. Seed treatment with formazan or carbofuran coating, or using 3% carbofuran granules at 1.5–2 kg per 667 m², can provide long-term protection against planthoppers. Insecticides such as 80% dichlorvos EC, 40% omethoate EC, 40% monocrotophos EC, 50% phoxim EC, and 50% methamidophos EC should be applied to corn fields and surrounding weeds during planting and seedling stages. Special formulations like 2% Inabajing wettable powder and 50% Bazaar EC are also effective. At the seedling stage, diseased plants should be removed and burned immediately. Spraying 1.5% spirit solution (800–1000 times dilution) or 20% A500 can help reduce disease incidence. Additionally, increasing organic fertilizer use, applying balanced N, P, K, and micronutrients, and timely soil cultivation promote healthy plant growth and enhance resistance to disease.
Corn rough dwarf disease is highly destructive, and once infected, plants cannot fully recover. Spraying pesticides on already infected plants is not an effective solution. However, combining agricultural and chemical control methods can effectively manage the disease. Since the disease is entirely caused by the transmission of the planthopper, focusing on its control is key to preventing outbreaks. The first generation of planthoppers is the main cause of corn damage. Farmers should take proactive steps to prevent both corn borers and rough dwarf disease, ensuring high yields and quality harvests.
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