Abstract
The effects of three synthetic chemicals at recommended dosages on disease incidence, severity and total damage by the beetle-transmitted okra mosaic virus (OMV) were compared with those of natural extracts from the seeds of neem, Azadirachta indica. Only treatments with the synthetic pyrethroid, lambdacyhalothrin, at 15 g a.i. ha-1 and aqueous neem solution at 467 I ha-1 significantly (P ? 0.05) reduced incidence severity and total damage. Treatments with a cypermethrin + dimethoate mixture (3:25) at 280 g a.i. ha-1apparently had the same effect on disease incidence and severity, but it had no effect on total damage relative to the untreated control. In all cases, the effects of neem oil at 60 I ha-1 and carbaryl at 85 g a.i. ha-1 were not significantly different from the control. Lambdacyhalothrin and aqueous neem solution are easily degraded by metabolizing systems. However, the latter may be less expensive than synthetic chemicals in areas where neem seeds are readily available and the extraction process is cheap.
