Reducing pesticide costs using tungro resistant rice varieties
1999
Villar, A.C.
Field experiments were conducted for two cropping seasons to determine the efficacy of chemical control and resistant varieties against the tungro virus disease. Tungro virus symptoms were observed on susceptible IR64 variety 5 days after transplanting. Symptons were yellowing of the leaves, reduced tillering and stunting. Spraying insecticide Cypermethrin of susceptible variety did not reduce the disease onset and disease incidence of the tungro disease, while intermediate and resistant varieties, IR60, IR72, IR74 and PSB Rc 18 showed a very low disease incidence ratings and longer disease onset. Cypermethrin did not affect green leafhopper population count. However, climate had influenced its population, highest number of individuals were observed during the low rainfall in the 1998 dry season than the 1997 wet season. General observation on the crop stand or agronomic plant characteristics showed that sprayed susceptible IR64 variety had very poor plant characteristics than the intermediate and resistant varieties. Futhermore, yield and yield components of sprayed and unsprayed IR64 were low, as compared to intermediate and resistant varieties which showed significantly higher yields. As a result, higher net profits were obtained on resistant varieties. The highest were observed on PSB Rc 18 (P26,585.00) during the dry season, while a negative profit or a yield loss of P6,357.00 per cropping were obtained on treatments of sprayed and unsprayed susceptible variety. This study implies that insecticide Cypermethrin was not effective in controlling green leafhopper population and reducing tungro disease infection. Thus, the use of resistant varieties is more advantageous and profitable
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