Gamma Irradiation as a Phytosanitary Treatment of Bactrocera tau (Diptera: Tephritidae) in Pumpkin Fruits.

The fruit fly Bactrocera tau (Walker) is an important quarantine pest that damages fruits and vegetables throughout Asian regions. Host commodities shipped from infested areas should undergo phytosanitary measures to reduce the risk of shipping viable flies. The dose-response tests with 1-d-old eggs and 3-, 5-, 7-, 8-d-old larvae were initiated to determine the most resistant stages in fruits, and the minimum dose for 99.9968% prevention of adult eclosion at 95% confidence level was validated in the confirmatory tests. The results showed that 1) the pupariation rate was not affected by gamma radiation except for eggs and first instars, while the percent of eclosion was reduced significantly in all instars at all radiation dose; 2) the tolerance to radiation increased with increasing age and developmental stage; 3) the estimated dose to 99.9968% preventing adult eclosion from late third instars was 70.9 Gy (95% CL: 65.6-78.2, probit model) and 71.8 Gy (95% CL: 63.0-87.3, logit model); and iv) in total, 107,135 late third instars cage infested in pumpkin fruits were irradiated at the target dose of 70 Gy (62.5-85.0, Gy measured), which resulted in no adult emergence in the two confirmatory tests. Therefore, a minimum dose of 85 and 72 Gy, which could prevent adult emergence at the efficacy of 99.9972 and 99.9938% at the 95% confidence level, respectively, can be recommended as a minimum dose for phytosanitary treatment of B. tau in any host fruits and vegetables under ambient atmospheres.

Methyl bromide as a quarantine treatment for Chlorophorus annularis (Coleoptera: Cerambycidae) in raw bamboo poles.

At least 26 different species of insects of quarantine significance were intercepted from 1985 to 2005 on bamboo (Bambusa spp.) garden stakes from China. Three fifths of the live insects were cerambycids in nine genera, including Chlorophorus annularis F., the bamboo borer. The current APHIS-PPQ treatment is fumigation schedule T404-d, which requires high doses of methyl bromide (MeBr) for 24 h. No specific fumigation data exist for C. annularis. Chinese and American quarantine scientists cooperated in testing to determine whether this schedule, or lower doses, would be effective as a quarantine treatment for C. annularis infesting dried bamboo poles. A lower dose based on APHIS tests for solid wood packing (SWP) failed (3/511 survivors) at 56 g/m3 for 24 h at 10.0 degrees C. We therefore tested five progressive doses at five temperatures intermediate between the lower SWP schedule and the much higher applied doses (e.g., 120 g/m3 for 24 h at 10.0 degrees C) of schedule T404-d. Fumigations of infested bamboo poles conducted in 403.2-liter chambers with 52% vol:vol loading at doses of 48, 64, 80, 96, and 112 g/m3 at 26.7, 21.1, 15.6, 10.0, and 4.4 degrees C, respectively (20 total replicates, with 4 replicates per dose), had no survivors among 2,847 larvae, 140 pupae, and 122 adults. Control replicates (three) had a total of 455 live stages (397 larvae, 31 pupae, and 27 adults). Tests conducted with a sea/land cargo container loaded to 80% capacity with bamboo poles verified the ability of the schedule to maintain effective concentrations over 24 h in commercial-sized fumigations. We propose a new bamboo quarantine treatment schedule at reduced rates of applied MeBr.