Rice stripe disease is a viral infection that affects rice plants, especially during the seedling stage. The initial symptoms include chlorotic yellow and white spots at the base of the heart leaves, which gradually develop into yellow stripes running parallel to the leaf veins. Between these stripes, the tissue remains green. Different rice varieties show varying levels of susceptibility. For example, indica and japonica rice may display yellow or white, soft, curled, drooping, or even dry-hearted symptoms, while dwarf japonica rice might not exhibit a "dead heart" appearance but instead shows yellow-green interveinal patterns, reduced tillering, and earlier withering of infected plants.
In the early stages of infection, yellow spots appear at the base of the next leaf, expanding into irregular yellow-white streaks. At this point, the leaves are usually not severely affected. Once the plant reaches the jointing stage, yellow-green stripes may only appear on the lower part of the flag leaf, leading to heading malformations and reduced grain production. This highlights that the earlier the infection occurs, the more severe the damage and the greater the yield loss.
To manage rice stripe disease, it's crucial to focus on controlling its vector, the Laodelphax striatellus (small brown planthopper). Since the virus can only be transmitted by this insect, prevention strategies should emphasize "pest control for disease prevention" and "cutting off the source of infection." Given that the first, second, and third generations of adult planthoppers migrate into fields and create three peak infestation periods, multiple stages of intervention are necessary to effectively manage the disease.
Early intervention is key, as the earlier the virus infects the plant, the more severe the impact. Therefore, the strategy of "protecting before infection" is recommended. Chemical control typically starts in mid-June, focusing on managing Laodelphax striatellus during the seedling phase. Recommended insecticides include Insectrophos-methyl, pyriprodil, chlorpyrifos, fipronil, or their combinations.
For foliar sprays, it’s important to apply treatments when the rice enters the tillering stage. Effective options include imidacloprid, chlorpyrifos (long-acting formulation), fipronil (Frigidol), isoprocarb (Yefei San), thiamethoxam, buprofezin, and avermectin. To prevent resistance development, it's advisable to rotate between different insecticides. Those with longer residual activity, such as pyridones, fipronil, thiamethoxam, and imidacloprid, are recommended for sustained control, while others like chlorpyrifos, isoprocarb, aldicarb, and dichlorvos provide quicker knockdown effects.
Seed treatments with imidacloprid or fipronil can also help protect young plants from early infections. In the early stages of the disease, applying chlorobromoisocyanuric acid (a disinfectant) and Ningnanmycin (a bacterial inoculant) may help reduce symptom severity and limit viral spread.
Additional cultural practices play a vital role in disease management. These include plowing and irrigation, removing weeds from the field and roadside areas, and avoiding proximity to wheat and corn fields to minimize virus sources. Delaying sowing dates, planting resistant rice varieties, and improving soil fertility by increasing phosphorus and potassium levels are also essential components of an integrated pest management approach.
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