Tomato yellow leaf curl virus (TYLCV) is the most frequently occurring virus in tomatoes in the Middle East, and the most harmful one. It is transmitted solely by the whitefly Bemisia tabaci (Gennadius). Within 4-6h of inoculative feeding, a whitefly can transmit TYLCV to a healthy plant with 80% probability. The symptoms are apparent after two to three weeks whereupon fruit-set is effectively terminated. The only means of controlling TYLCV is by controlling the whitefly. Until 1990 this was exclusively by insecticides. Starting in 1990, growers of greenhouse tomatoes in Israel began adopting insect exclusion screens to prevent inoculation of TYLCV. This article reports on the methods used in the search for efficient screening materials and presents data on their relative efficiencies in excluding B. tabaci and several other greenhouse pests. Ten materials were tested, of which five were found to be effective in excluding B. tabaci under laboratory conditions. This number was reduced to three following field trials and trials in commercial tomato greenhouses. These materials are now in widespread use in Israel: by 2000 practically all table tomatoes in Israel were grown under exclusion screens. The use of exclusion screens has been shown to be an economically viable pest management method.

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In order to test the hypothesis that the forebrain is involved in controlling acoustically guided behaviour, we carried out behavioural studies in combination with brain lesions, neuroanatomical and electrophysiological experiments in males and females of different species of frogs. Whereas the dorsomedial pallium plays no or only a minor role, the striatum, the septum, and the preoptic area potentially influence the behaviour because they send parallel descending projections to different premotor and motor networks in the brainstem. These parallel projections may be the basis for the variability seen in the behaviour.

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