A Note on the Biology of Calidea Dregei Germ

Abstract

Calidea dregei is well known as a stainer of cotton. Considerable variations in the extent of damage by the bug are found in different varieties of sorghum. A large range of types has been examined and certain general features stand out. Those types having the seed enclosed to a large extent by the glumes exhibit the greatest degree of resistance to the pest and a general tendency of quick maturity strains to be less heavily damaged is noticeable. This latter factor is probably due to the short season types being exposed to attack for a shorter length of time than longer season varieties. Thus the open-headed, quickly maturing, Shallu types with the seed almost completely protected show an average percentage of damaged seed from three experiments of II per cent in comparison to the longer season Milo types, such as Martins SA. 5330, with the seed almost completely exposed which gives an average of 26 per cent damaged seed. C. dregei shows a very marked resistance to the commoner insecticides in the field. In laboratory scale trials a number of insecticides were tested against the pest. A much greater susceptibility to insecticides of plant origin was shown.