Residual Toxicity of Synthetic and Bio-Insecticides Sprayed on Okra against Whitefly (Bemisia Tabaci [Genn.])

Abstract

In order to compare residual toxicity of synthetic and bio-insecticides sprayed on okra against whitefly (Bemisia tabaci Genn.), the experiment was conducted at the experimental site, Poonch University of Agriculture Rawalakot (AJK) during 2016. The crop was sprayed with five synthetic pesticides including Tracer (Spinosad), Runner (Methoxyfenozide), Radiant (Spinetoram), Belt (Flubendiamide) and Coragen (Chlorantraniliprole) as well as eight botanical pesticides based on Neem (Azadirachta indica), Tobacco (Nicotiana tabacum), Tooh (Citrullus colocynthus (L.) Schrad), Datura (Datura stramonium), Garlic (Allium sativum L.), Eucalyptus (Eucalyptus obliqua, E. occidentalis) and Ginger (Zingiber officinale). The determined dissipation response of these synthetic and botanical pesticides their toxic residual effects on edible okra pods were recorded upto 2 weeks of spray. The toxic residues of Tracer (EUMRLs = 0.015 mg/kg-1); Runner (EU-MRLs=0.05 mg/kg-1), Belt (EU-MRLs= 0.01 mg/kg-1) persisted upto 7 days after spray; while Radiant (EU-MRLs=0.025 mg/kg-1) showed strong persistence of high residual toxicity upto 14 days of spray. However, Coragen showed toxic residues below EU-MRLs (0.60 mg/kg-1) after 3 days of spray. Extracts of neem, tobacco and tooh/tumma were more effective against whitefly compared to Datura, Garlic, Eucalyptus and Ginger extracts. The neem based bio-insecticides were more effective to inhibit whitefly population; while tobacco, tooh/tumma and ginger extracts also suppressed whitefly population considerably. Although chemical control was most effective to combat whitefly population, but for a crop that is harvested for its edible pods almost daily or at alternate day, the use of these poisons is extremely harmful for human health. The botanical extracts suppressed whitefly population appreciably and pods from the sprayed plots were free of any toxic effects on the next day of spray.