Frequency and timing of insecticide application to control rice tungro virus (RTV)
1987
Valencia, S.L. | Mochida, O. (International Rice Research Inst., Los Banos, Laguna (Philippines). Entomology Dept.)
When vector populations are high, using insecticides to control RTV [rice tungro virus] infection in moderately resistant and susceptible cultivars requires increasing the number of applications. More precise timing of insecticide application could reduce the number of applications needed. Two trials were conducted during the 1986 wet season to test insecticide timing and application frequency. IR64 (resistant) and TN1 (susceptible to green leafhopper and RTV) were planted in 5- x 7-m plots with 4 replications. The seedbeds were covered by mesh to prevent early RTV infection. In the first trial, cypermethrin (0.05 kg ai/ha) and monocrotophos (0.4 kg ai/ha) were applied 4 times at 10-d intervals starting at 1, 5 or 10 d after transplanting (DT). RTV infected hills were recorded at 60 DT. RTV incidence was significantly lower on IR64 and TN1 with cypermethrin applied within 5 DT. Monocrotophos applied 1 DT gave control only on the resistant cultivar. In the second trial, three insecticides were used on moderately resistant IR42. Cypermethrin at 0.05 kg ai/ha and monocrotophos and MIPC at 0.41 kg ai/ha were sprayed 2,3, and 4 times at 10-d intervals starting 5 DT. Three applications protected the seedlings.
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