2011 Annual Report
1a.Objectives (from AD-416)
Determine an effective radiation dose to control invasive pests in exported commodities.
1b.Approach (from AD-416)
Dose response tests to determine most radio-tolerant stage, followed by large-scale validation tests with most tolerant stage. Submit data to APHIS for treatment approval.
The effects of irradiation on egg, larval, and pupal development, and adult reproduction in light brown apple moth were examined. Eggs, neonates, early instars, late instars, early pupae and late pupae were irradiated at target doses of 60, 90, 120, or 150 Gy or left untreated as controls in replicated factorial experiments and survival to the adult stage was recorded. Tolerance to radiation generally increased with increasing age and developmental stage (Table 1). A radiation dose of 120 Gy applied to neonates and early instars prevented adult emergence. A dose of 150 Gy prevented adult emergence in larvae at all stages. In large-scale validation tests, a total of 34,997 fifth instars irradiated at a dose of 150 Gy in diet, apples or peppers produced no adults. Pupae were more radiotolerant than larvae, and late stage pupae were more tolerant than early stage pupae. Adults from late stage pupae irradiated at 300 Gy laid <3% fertile eggs, and adults from late stage pupae irradiated at 350 Gy produced no fertile eggs. Current work with light brown apple moth involves large-scale validation testing of pupae at 350 Gy.
For most commodities, the fifth instar is the most radiotolerant life stage likely to be associated with the commodity, and a minimum radiation dose of 150 Gy will prevent adult emergence from this stage. For commodities such as table grapes that may contain pupae, a radiation dose of 350 Gy may be necessary to sterilize emerging adults and this would be an effective all-crops irradiation treatment for light brown apple moth. Progress is monitored through meetings, telephone and e-mail communications.