Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/24/1997
Publication Date: N/A
Citation: Interpretive Summary: Diamondback moths are a serious pest on many vegetable crops. Natural compounds obtained from sweetpotato tissues were shown to cause a considerable decrease in growth and survival of the insect's larvae. These compounds (glycosides) were previously shown to interfere with growth of weeds and fungi. The natural compounds in question will be considered in experiments aimed at replacement of methyl bromide treatments. Since considerable differences in glycoside contents occur between sweetpotato genetic resources, breeding efforts will increase these contents.
Technical Abstract: Storage root periderm tissue of the sweetpotato, Ipomoea batatas (L.) Lam. cv. Regal, was sequentially extracted with hexane, dichloromethane and methanol. Extracts were incorporated in a meridic diet for diamondback moth, Plutella xylostella (L.) larvae. Second instar larvae were exposed to the diet for five days, after which time growth and survival were determined. Antibiosis was found in the methanol fraction only. This fraction was further separated by low pressure column chromatography into five fractions, two of which promoted growth signficiantly and one caused significant decreases in both growth and survival. The inhibitory fraction was further purified with HPLC methods. A single fraction, consisting of a mixture of closely related resin glycosides, was responsible for antibiosis. The estimated LD50 was 7.2 mg per ml diet. At that concentration the remaining larvae showed a decrease in weight of 46%. Fifty percent reduction of total 'live' weight was found at 4.2 mg per ml diet.