Occurrence and Control Methods of Rice Dwarf Disease in Japonica Rice

I. Damage Symptoms

The rice plant becomes stunted, with increased tillering, dark green leaves, and transparent yellowish-white dashed line streaks on young leaves and leaf sheaths. When the disease occurs at the seedling stage, tillering is reduced and the plant cannot head; when it occurs after booting, yellowish-white streaks appear only on the flag leaf or other leaf sheaths, and late-onset plants mostly produce neck-enclosed heads, small heads, many empty and shriveled grains, and a low seed-setting rate.

II. Preventive Measures

Once japonica rice contracts dwarf disease, it is very difficult to cure, so comprehensive preventive measures should be actively adopted.

1. Select disease-resistant and disease-tolerant varieties. Select and breed varieties with relatively mild incidence according to local conditions to reduce the disease incidence rate.

2. Improve cultivation techniques. Reasonably adjust the rice sowing and transplanting periods so that the growth stages in which japonica rice is highly susceptible avoid the peak migration periods of virus-transmitting insects. Appropriately increase transplanting density, strengthen fertilizer and water management, promote early rapid growth of seedlings at the early stage and vigorous growth at the middle stage, enhance disease resistance, and reduce damage.

3. Maintain field sanitation. Timely remove weeds along field edges to reduce places where leafhoppers shelter.

4. Strengthen fertilizer and water management. Apply sufficient basal fertilizer, apply topdressing early, do not blindly apply excessive nitrogen fertilizer, prevent excessive vegetative growth and delayed maturity, reduce the number of attracted insects, and improve disease resistance. Achieve thin-water transplanting and shallow-water irrigation to reduce the natural parasitism rate of green rice leafhopper eggs.

5. Vigorously control diseases and pests. Seize the two peak migration periods of the green rice leafhopper for control. Use 1.5-2.0 kg of 3% carbofuran granules, mix with 20 kg of dry fine soil, and broadcast it on the seedling board after rice sowing; after the seedlings turn green, for every 667 sq m (1 mu), use 100 ml of 50% metolcarb emulsifiable concentrate and 150-200 ml of 20% isoprocarb emulsifiable concentrate, dilute with 40-50 kg of water, and spray evenly, applying once every 5-7 days for two consecutive sprays. During the seedling stage in the field, frequently go deep into the field, continuously check the occurrence quantity of the green rice leafhopper in the paddy field, and apply pesticide at the appropriate time and amount. For every 667 sq m, use 20 g of 25% pymetrozine, dilute with 40-50 kg of water, and spray evenly, with remarkable results. During the growth period of japonica rice, also always pay attention to the occurrence of the green rice leafhopper, and timely kill the virus-carrying vectors to completely eliminate the occurrence of the disease.