The Western flower thrips (WFT), Frankliniella occidentalis (Thysanoptera: Thripidae) (3), was described by Pergande in 1895 (6). It is distributed throughout North America (3,7) and is the most prevalent species of thrips attacking floriculture throughout the USA (7). In 1985 it appeared in Scandinavia and Germany (8) and in 1987 in Israel (1), probably introduced with chrysanthemum buds from Western Europe. It subsequently spread rapidly in Israeli fields and glasshouses, causing severe damage to many crops. No satisfactory control of WFT by conventional insecticides has been achieved in this country (M. Gokkes, personal communication; 2). In the USA WFT rapidly developed resistance to organophosphors, carbamates and pyrethyroids (7). It was therefore deemed necessary to investigate the efficacy of nonconventional pesticides against WFT, with emphasis on neem (Indian lilac; Azadirachta indica A. Juss) formulations, the insecticidal properties of which have been reviewed lately (e.g. 4,5). Two products were included in this study: a dried methanolic neem seed kernel extract (NSKE) prepared by us; and Azatin (Agridyne Co., Salt Lake City, UT), containing 3% azadirachtin and, inter alia, 4% naphthalene (w/w), 2% butanol (w/w) and petroleum distillates as solvent. The dried NSKE was diluted with 80% methanol prior to spraying, whereas the Azatin formulation was diluted with water containing 7 drops of Triton X-100 per 50 ml. Bo products, diluted to concentrations in the range of 0.01-1%, were sprayed to runoff with Desaga spray gun (Desaga Co., Heidelberg, Germany) on young cotton seedlings in the cotelydon stage in plastic containers. Two experimental setups were used: (i) In a pretreatment infestation, females were allowed to oviposit during 24 h on the seedlings, and then removed. When the eggs were 2-3 days old, the seedlings were sprayed with the neem formulations. (ii) In a posttreatment infestation, females were given access to seedlings that had been sprayed on the previous day, allowed to oviposit during 24 h and then removed. Adult mortality in the posttreatment setup, and egg hatch, development of nymphs, pupation and emergence of adults in both setups were recorded. All experiments were conducted at 20 +/- 2-degrees-C. The results showed that neither preparation brought about adult female mortality or reduced fecundity in the postreatment setup or affected egg hatch in either setup. Whereas even 1% NSKE was ineffective against nymphs in both setups, Azatin at low concentrations prevented the development from the first to the second nymphal instar. Although inactive at 0.5% in both setups against the first nymphal instar - apart from prolonging it by 2 days -at 0.1% in the pretreatment and at 0.5% in the posttreatment setup, very few nymphs developed from the first to the second instar, and those that did - died soon afterwards. No second instars developed at 0.5% in the pretreatment setup. In the controls the seedlings suffered severe damage due to thrips' feeding, whereas seedlings treated with as little as 0.01% Azatin showed some slight damage but recovered fully after die death of the nymphs. Azatin was supplied by C.T.S. Ltd, Tel Aviv, Israel.The research was supported by the U.S.-Israel Cooperative Development Research (CDR) Program, grant C7-006, U.S. Agency for International Development (AID).
