Gamma irradiation quarantine treatment against blueberry maggot and apple maggot (Diptera: Tephritidae).
The criterion for efficacy of irradiation disinfestation treatments against tephritid fruit flies has been prevention of adult emergence. Although this technique has worked well for tropical tephritids that do not diapause, it is difficult to apply to diapausing insects that must be brought out of diapause by lengthy and not entirely successful procedures. Therefore, a more reliable method of measuring efficacy of irradiation quarantine treatments against diapausing tephritids is needed. Some Tephritidae are known to diapause as phanerocephalic pupae. Accordingly, that would be the latest stage that could be used to determine efficacy without the complications posed by estimating diapause survival. Prevention of the phanerocephalic pupa at the 99% level was accomplished with an estimated 58 and 24 Gy for the apple maggot, Rhagoletis pomonella (Walsh), and the blueberry maggot, Rhagoletis mendax Curran, respectively, when irradiated as 3rd instars in fruits. Adult apple maggot emergence was prevented with an estimated 15 Gy, which was 26% of the dose required to prevent pupation to the complete phanerocephalic stage. Prevention of the phanerocephalic pupa can be determined ∼6 days after pupariation at ambient temperatures, making it possible to adjust research parameters during a limited season, such as when working with the blueberry maggot, which is available in the field in blueberries from late July to early September. Although basing efficacy of irradiation quarantine treatments against diapausing tephritids on prevention of pupation will result in substantially higher doses than basing efficacy on prevention of adult emergence, the research can be done more rapidly and with greater confidence, and many temperate fruits, including blueberries and apples, tolerate much higher radiation doses than those required to prevent pupation of tephritids.