Susceptibility of Maconellicoccus hirsutus (Homoptera: Pseudococcidae) to methyl bromide.

Eggs, crawlers, early nymphs, late nymphs, and adults of the pink hibiscus mealybug, Maconellicoccus hirsutus (Green), were tested for their susceptibility to methyl bromide in 2-h laboratory fumigations at ambient conditions (25 degrees C, 95% RH). Dose-response tests indicated that the egg was the most susceptible life stage with an LC99 of 20.2 mg/liter. Based on probit analysis of dose-response data, no significant differences were observed among susceptibilities of the crawler, early stage or late stage nymphs, or adults at either the LC50 or LC99 level, but late stage nymphs were more tolerant than early stage nymphs in a separate paired comparison test. Confirmatory tests showed that a dose of 48 mg/liter methyl bromide, the USDA-Animal Plant Health Inspection Service treatment dose schedule for mealybugs at 21-26 degrees C, produced 100% mortality of all life stages. On the basis of these results, we conclude that the methyl bromide treatment schedule for mealybugs will provide quarantine security for M. hirsutus infesting commodities for export or import.