Cotton Allelochemics and Growth of Tobacco Budworm Larvae1

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Abstract
Eight alleged allelochemics that naturally occur in cotton, Gossypium hirsutum L., or as a constituent part, were added to a commercial wheat‐germ diet at various concentrations. Neonate larvae of tobacco budworm [Heliothis virescens (F.)] were allowed to feed for 5 days and then weighed to determine the effects of allelochemics on larval growth. Regression equations were fitted to the data. A linear regression in the form Y = a + bX described the relationship for cyanidin, delphinidin, and gossypol up to 0.20% in the diet. A curvilinear regression equation in the general form of Y = aXb described the relationships for catechin, condensed tannin, chrysanthemin (cyanidin ‐3‐β‐glucoside), isoquercitrin, and quercetin. These were fed at higher levels (up to 1%) than the three allelochemics fitted with the linear regression equation. The level of each allelochemic in cotton required to reduce larval weight 90% is within the range of the amounts found in various cotton strains and primitive accessions. All except gossypol are found in several plant families and may thus be useful in developing plant resistance to tobacco budworm in several plant families. Several species of Heliothis are pests of economic importance worldwide.