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In a food preference chamber, fewer adults of red flour beetle (Tribolium castaneum Herbst) settled in rice grain treated with 100, 500, or 1,000 ppm of the oil of turmeric Curcuma longa (L.), sweetflag Acarus calamus (L.), or neem Azadirachta indica A. Juss, or "Margosan-O" (a commercial neem-based insecticide). Repellency increased with increasing concentrations of the oils and Margosan. In another choice test, filter paper strips treated with turmeric oil or sweetflag oil at 200, 400, or 800 JLg/cm 2 repelled insects during the first2 wk; thereafter, repellency decreased more rapidly than with neem oilor Margosan-O. Tribolium castaneum adults fed wheat flour, which had been treated with the test materials at 200 ppm, produced fewer and underweight larvae, pupae, and adults compared with the control.

Certain physicochemical stresses affect the susceptibility of plants to insects. The objective of this study was to determine the effects of different levels of Fe, Si, and Al on the establishment of Sogatella furcifera (Horvath) on resistant IR2035-117-3 (IR2035) and susceptible Taichung Native 1 (TN1) rice (Oryza saliva L.) cultivars under glasshouse conditions in natural daylight of 12 h, 29/21 °C (day/night), and minimum 70% relative humidity. Insect population increased on rice plants grown in culture solution containing low (0.02 mg L~') or high (40 mg L~') Fe than on plants grown in standard culture solution (Fe at 2 mg L~'). Increased Si (400 mg L-') reduced intake and assimilation of food, growth, adult longevity, fecundity, and population increase by 5. furcifera on susceptible TN1 plants.

Both in a choice and multi-choice laboratory tests, fewer adults of the banana root borer, Cosmopolites sordidus (Germar), settled under the corms of the susceptible banana "Nakyetengu" treated with 5% aqueous extract of neem seed powder or cake or 2.5 and 5% emulsified neem oil than on water-treated corms. Feeding damage by larvae on banana pseudostem discs treated with 5% extract of powdered neem seed, kernel, or cake, or 5% emulsified neem oil was significantly less than on untreated discs. The larvae took much longer to locate feeding sites, initiate feeding and bore into pseudostem discs treated with extract of powdered neem seed or kernel. Few larvae survived when confined for 14 d on neem-treated banana pseudostems; the survivors weighed two to four times less than the larvae developing on untreated pseudostems. Females deposited up to 75% fewer eggs on neem-treated corms. In addition, egg hatching was reduced on neem-treated corms. The higher the concentration of neem materials the more severe the effect.

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