Identification of feeding stimulants for boll weevils from cotton buds and anthers

Column chromatography of the pentane extract of freeze-dried cotton buds or anthers yielded a wax-sterol ester fraction that exhibited potent feeding stimulant activity for the cotton boll weevil. The waxes of the wax-sterol ester mixture were responsible for the feeding activity. Saponification of the wax-sterol ester fraction yielded about 15% alcohols and 85% sterols. A C18∶1 alcohol, dihydrophytol, phytol, and geranylgeraniol constituted 15, 36, 26, and 23%, respectively, of the total alcohols, implicating certain of their long-chain esters as feeding stimulants. Several esters of dihydrophytol, phytol, and geranylgeraniol were identified among the waxes by GC-MS. Certain phytol, geranylgeraniol, and oleyl alcohol esters containing C12 to C26 acid moieties were synthesized and were found to induce high feeding stimulant activity in the cotton boll weevil.