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1. Rice yellow dwarf disease is characterized by general chlorosis, with pronounced stunting and profused tillering. The chlorotic leaves are uniformly pale yellow. The young infected plants usually produce either no panicle at all or a few small panicles with unfilled grains. Plants infected during later growth stages may not develop symptoms before harvest.
2. This disease is caused by phytoplasmas and these are generally Observed in phloem tubes of yellow dwarf infected rice plants. These are pleomorphic bodies measured from 80-800 mm, devoid of cell walls and bound by unit membrane.
3. The disease is transmitted by leafhopper, Nephotettix virescens. The insect can acquire the pathogen by feeding on diseased plant by half an hour and require long incubation period (20 days) to transmit the phytoplasma.
4. The insects remain infected until they die. A combination of low temperature and high humidity favours the leafhopper population resulting in higher disease incidence. The ratoon plants growing from stubble may be diseased and act as inoculum sources for later infections.
The yellow dwarf of rice may be reduced by:
• Field sanitation
• Seed treatment with Carbofuran and subsequent soaking in Carbofuran solution (75% WP) for 36 hours prior to transplanting (by effectively controlling the vector)
• Spraying Dimecron (0.03%), Carbofuran (0.04%), Dimethoate (0.025%) and Methyl Dometin (0.025%) Spraying of ch lorotetracycline at 100 ppm