EFFECT OF LEVEL OF SEED INFESTATION ON MORTALITY OF LARVAE AND PUPAE OF CALLOSOBRUCHUS-MACULATUS (F) (COLEOPTERA, BRUCHIDAE) IN SOME CONTROLLED ATMOSPHERES

Blackeye cowpea seeds of fairly uniform weight were infested with Call osobruchus maculatus (F.). Seeds containing 10-12 larvae or pupae per seed (high infestation) and those containing 1-2 larvae or pupae per s eed (low infestation) were exposed to 70% CO2 in air, 30% CO2 in air, 1% 02 in N2 and 4% 02 in N2 atmospheres respectively, at 27 +/- 2-degr ees-C and 70 +/- 5% r.h. In the different atmospheres, larval and pupa l mortality was generally higher in seeds with low infestation than in seeds with high infestation. Insect mortality was not significantly d ifferent between treatments involving 70% CO2 in air and 1% 02 in N2; and between treatments involving 30% CO2 in air and 4% 02 in N2, irres pective of level of insect infestation in seeds. The results are discu ssed in relation to practical application of controlled atmospheres fo r stored-products protection.