Tomato leaf miner, Tuta absoluta Meyrick (Lepidoptera: Gelechiidae), is one of the most destructive pests of tomato in many parts of the world including Iran. Field studies were conducted to determine the short and long term effects of Bacillus thuringiensis var Kurstaki (Bt), azadirachtin (AZ), a mix of AZ + Bt, and indoxacarb, as a current chemical insecticide, on T. absoluta larvae. Also, effects of the insecticides were studied on the coexisting generalist predators, Coccinella septempunctata L., Chrysoperla carnea Stephens and Syritta sp. Sampling of T. absoluta and its coexisting generalist predators were performed 1 day before treatment (DBT) and one, 5, 8, 14 and 19 days after treatment (DAT). The results indicated significant short term effect of indoxacarb on the pest larvae. Indoxacarb reduced T. absoluta density and damages. Bt, AZ and mixture of them significantly suppressed the larval density at 19 DAT and caused significant reduction in leaf, stem and fruit damage. The highest long term effect on the pest abundance and damage were observed in Az + Bt caused 100% reduction in fruit and foliage damage compared to the control. The highest and lowest adverse effects on C. carnea, C. septempunctat and Serrita sp. were observed in indoxacarb and Bt treatments, respectively. Findings of this study imply that the mixture of Az + Bt has the highest selective toxicity on the pest and the lowest effect on its coexisting generalist predators.

The anthocorid bugOrius albidipennisReuter is a generalist predator that feeds on the whiteflyBemisia tabaciGennadius and the strawberry spider miteTetranychus turkestaniUgarov & Nikolski in greenhouse crops. There are no previous studies on the potential efficacy of the predatory bug against these pests on greenhouse crops. We report on the efficacy and the prey preference of the predator to control these pests on different host plants under laboratory conditions. In a laboratory experiment, we estimated the predation rates ofO. albidipennisat different densities of each prey after 24 h on cucumber and sweet pepper leaves. Predation rates of the predatory bug toT. turkestaniandB. tabaciwere significantly higher on sweet pepper leaf than on cucumber leaf. We studied the effect of plant species on prey preference and switching ofO. albidipennistoB. tabaciandT. turkestaniusing Manly'sαindex values and Murdoch's no-switch line, respectively. Our results show thatO. albidipennisprefersT. turkestanitoB. tabacion both host plants but its preference forT. turkestanion sweet pepper is significantly greater than on cucumber. Moreover, on sweet pepper, preference values are completely fitted by Murdoch's no-switch line. The findings suggest that morphological defence traits of plants, such as hairy leaves of cucumber, may effectively change prey preference and reduce predation success ofO. albidipennis.

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