METHODS OF INFESTATION OF SORGHUM LINES FOR THE EVALUATION OF RESISTANCE TO THE MAIZE WEEVIL, SITOPHILUS-ZEAMAIS MOTSCHULSKY (COLEOPTERA, CURCULIONIDAE)

The effects of age ranges, female density, and oviposition periods on the development of maize weevil (MW), Sitophilus zeamais Motschulsky, were studied on sorghum, Sorghum bicolor L. grain under controlled tem perature, R.H. and photoperiod, in order to select a reliable and effi cient infestation method for resistance screening of sorghum against M W. Females between 16 and 20 days old had a significantly larger ovipo sition rate than the other age ranges studied. The total number of MW eggs increased significantly with an increase in the number of seeds, weevil density and oviposition period, but these differences were not reflected on the progeny and kernel weight loss. This response was sim ilar using three or four MW females and 14 or 21 days oviposition. The se MW densities and oviposition periods produced significantly more pr ogeny and kernel weight loss than two females ovipositing during 7 day s. The percentage damaged grains increased significantly with a decrea se in the number of seeds and an increase in the number of weevils and oviposition periods. Infesting 50 grains with three 16-20-day-old fem ales during a 14 day oviposition period appears to give a reliable den se distribution of the insects necessary to rank efficiently the sorgh um resistance against MW.