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Sugar Composition of Cotton Aphid and Silverleaf Whitefly Honeydews

D. L. Hendrix


 
ABSTRACT

Many of the sugars in the honeydew from the silverleaf whitefly (Bemisia argentifolii) and cotton aphid (Aphis gossypii) feeding upon upland cotton plants were identified. Both honeydews have been found to consist of several dozen oligomers of glucose and fructose. Both organisms produce these sugar mixtures from sucrose in their diet of cotton phloem. In both insects, most of the sugars in their honeydew are nonreducing and the vast majority of monosaccharides which make up these oligosaccharides are glucose. The sugar composition of these two honeydews are distinctly different. The most abundant sugar in silverleaf whitefly honeydew is the disaccharide trehalulose, an oligomer of sucrose. Cotton aphid honeydew contains only trace amounts of trehalulose but it contains large amounts of the trisaccharide melezitose. Neither of these sugars occurs in the cotton plant. Both insects create these sugar oligomers to counteract the osmotic stress of their diet and environment. One mechanism both insects utilize to overcome such stress is the conversion of some of the fructose from ingested sucrose into six carbon polyols. Whiteflies manufacture sorbitol from dietary fructose; aphids manufacture mannitol. Both honeydew formation and polyol formation are distinctly different in male and in female whiteflies.



Reprinted from Proceedings of the 1999 Beltwide Cotton Conferences pp. 47 - 51
©National Cotton Council, Memphis TN

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Document last modified Monday, Jun 21 1999