Effects of irradiation on Mexican fruit fly (Diptera : Tephritidae) larvaeinfesting grapefruit

A mean dose of 249.58 Grays (Gy) Co-60 irradiation caused greater than 99.9 968% mortality of 99 817 irradiated Mexican fruit fly, Anastrepha ludens (L oew) eggs and larvae which infested 'Ruby Red' (also called 'Webb Red Blush ') grapefruit (Citrus paradisi MacFayden), Determination was based on estim ated larval populations (number of pupae in control fruit) and pupal mortal ities (number of adults that eclose). Both Cs-137 and Co-60 required >15% d ose of irradiation to kill 99.9968% of 21-25 days-old larvae in the fruit c ompared to the dose required to kill eggs and larvae up to 17 days old. The LD(50)s of eggs and larvae up to 17 days of age and 21-25 days-old larvae were statistically similar based on estimated larval and pupal mortalities. The LD(50)s were 93 and 82% less for early stage and mature larvae, respec tively, than doses required for 99.9968% mortality.