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Prevention of Maize Virus Disease in Early Summer
Corn dwarf disease is a viral infection spread by the small brown planthopper (*Laodelphax striatellus*). Another significant viral disease affecting corn is maize dwarf mosaic, which differs from dwarf disease in its symptoms, vector, and management strategies. Maize dwarf mosaic typically causes mottled or streaked yellowing on the leaves, while dwarf disease leads to shortened internodes, resulting in stunted growth—often less than half the height of healthy plants. Affected plants may appear "dwarf-like," with curled leaves and distinct chlorotic spots along the leaf veins. These spots often start as small, white lines and gradually expand, while the main veins show waxy-white stripes. The remaining parts of the leaf tend to be dark green, stiff, and thick.
The severity of the disease depends on both the resistance of the corn variety and the timing of infection. Although the virus can infect corn at any stage, it is most dangerous during the early growth phase—especially before the 6-leaf stage. Infection after the 10-leaf stage tends to result in milder symptoms. This highlights the importance of early protection. Both viruses are insect-borne, but maize dwarf mosaic is transmitted by mites, while dwarf disease is carried by the small brown planthopper (SBPH). During winter, these vectors overwinter on weeds and in abandoned fields. Perennial weeds and crops like wheat also serve as reservoirs for the virus. As a result, weeds, aphids, and migratory locusts act as key sources of infection, spreading the virus into corn fields. Weather conditions that influence the survival and reproduction of these insects also play a major role in disease outbreaks.
To manage these diseases, an integrated approach combining pest control and disease prevention is recommended. First, planting resistant varieties suited to local conditions is crucial. Second, removing weeds along field edges and ditches promptly helps reduce virus sources. Third, proper crop management improves plant resilience—such as using plastic mulch, optimizing water and fertilizer use, and maintaining good field hygiene. Fourth, applying insecticides to control aphids and planthoppers is essential. Recommended treatments include 10% imidacloprid wettable powder diluted 3000–5000 times, 25% buprofezin wettable powder at 1000–1500 times, 4.5% cypermethrin emulsifiable concentrate at 1500–2000 times, or 5% fipronil at 30–50 ml per acre. Other options include 20% isoprovir EC at 150–200 ml, 48% chlorpyrifos at 100–120 ml, and 50% antifungal wettable powder at 6–8 g mixed with 50–60 kg of water. For already infected plants, early application of Ningnanmycin or foliar sprays can help reduce damage.
Timely spraying is critical. If the movement of pests can be predicted, treatment should begin a few days before or after their arrival. If not, focus on protecting seedlings and avoid delaying treatment until visible symptoms appear at the 9-10 leaf stage. Additionally, it's important to note that maize dwarf mosaic can be transmitted through seeds. Therefore, strict seed production management is necessary, and seeds should be produced in areas with low virus prevalence to minimize the risk of contamination and further spread.