| Scope and method of study. Laboratory and field experiments were conducted to evaluate the overall toxicity of neem extracts to the squash bug Anasa tristis De Geer (Hemiptera: Coreidae). Various extracts of neem Azadirachta indica A. Juss (Melliaceae) applied as foliar and soil treatments were compared to pure azadirachtin (the most active ingredient in neem extracts) to establish its role in their activity. Field experiments were used to evaluate the activity of these extracts under natural field conditions. Different concentrations of the toxins were used to establish dose-responses that were evaluated using a regression model.; Findings and conclusions. Colonization, mating and oviposition, were differentially affected by the various extracts of the toxin using different treatment methods. Oviposition and colonization among adults was affected by soil treatments but not foliar sprays. Although azadirachtin is the most active ingredient in neem, its activity is enhanced by other active components in these extracts. Neem extracts inhibited mating and oviposition. Treating males with neem extract resulted in occurrence of unfertilized eggs by accompanying females. Most of the field studies did not show significant dose responses. The insect populations were however higher among controls than the treatment ranges of 150, 300, 600ppm azadirachtin. |
