TOLERANCE OF IMMATURE STAGES OF FOUR STORED PRODUCT MOTHS TO METHYL-BROMIDE

Eggs, last instar larvae, and pupae of the pyralid moths, Ephestia elutella (Huebner), E. kuehniella Zeller, E. cautella (Walker) and Plodia interpunctella (Huebner) reared at 25.degree. C were exposed to methyl bromide over a wide range of concentrations and times at 10-30.degree. C. One laboratory stock, and 1 field stock of each species were tested, but differences between stocks of the same species were small. P. interpunctella required lower CT [concentration-time] products than the other species for complete kill of each stage. At 10.degree. C, larvae of the field stock of E. cautella required a CT product of 110 mg h/l for complete control. All stages of all species succumbed to a CT product of 64 mg h/l at 15.degree. C. When exposed at 20.degree. C or above, pupae aged 0-3 days were more tolerant than other stages. Eggs aged 2 days or over were more tolerant than younger ones. The fertility of survivors from fumigated eggs resembled that of controls, but that of some individuals fumigated as pupase was depressed. For fumigated eggs of E. elutella and P. interpunctella t 15.degree. C, the CT relationship held over concentrations from 4.2-10.8 mg/l and exposure periods from 1-16 h.