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The sweetclover root disk bioassay was used to test the activity of 21 sugars and related compounds as feeding stimulants for the sweetclover weevil Sitona cylindricollis Fähraeus. Of the compounds tested, sucrose was the most effective feeding stimulant. Compounds with moderate stimulant activity were fructose, glucose, galactose, mannose, myo-inositol, and maltose. Slightly active feeding stimulants included ribose, xylose, sorbose, and sedoheptulose. Arabinose, arabitol, mannitol, xylitol, cellobiose, raffinose, soluble starch, ascorbic acid, glucuronic acid, and glucosamine failed to exhibit feeding stimulant activity in these tests, Four compounds (arabinose. ascorbic acid, glucuronic acid, and mannitol) were tested for feeding deterrent activity, and all displayed such activity. Although the structural requirements for feeding stimulant or deterrent activity were not established. It was clear that small differences in chemical structure could cause large differences in feeding response.