PRELIMINARY EVALUATION OF IONIZING-RADIATION AS A QUARANTINE TREATMENT FOR THE FALSE GRAPE MITE, BREVIPALPUS-CHILENSIS

Fumigation with CH3Br, the most used quarantine treatment to control t he False grape mire, Brevipalpus chilensis Baker, a Chilean species oc casionally detected on table grapes and lemons for the U.S. market, af fects the atmospheric ozone. A study was carried our to determine the effects of 0.5, 1.0, and 1.5 kGy applied using a Cs-137 gamma irradiat or, combined with 24 h precold and 15 d at 0-2 degrees C (to simulate shipping from Chile to the U.S.), on viability of eggs, mortality of i mmatures and adults, and reproductive capacity of B. chilensis. Mites were irradiated on individual excised Ligustrum japonicum L. leaves ma intained on agar. Stages treated were 1-4 and > 4-day-old eggs, juveni les, and adults. All material was stored at 0-2 degrees C and 90 % RH during 15 days. Eggs of both ages were killed by 0.5-1.5 kGy followed by cold storage; older eggs were less susceptible than 1-4-day-old egg s. Some juveniles exposed to 0.5 kGy survived, indicating their relati vely lesser radiosensitivity compared to eggs; juveniles were more sus ceptible than adults. On day 1 after cold storage, 0.0, 0.5, 1.0, and 1.5 kGy caused 3.09 %, 83.79 %, 97.91 %, and 100.00 % mortality of adu lts, respectively. All adults were killed by 05 and 1.0 kGy on days 17 and 9, respectively. All irradiation treatments caused significantly greater adult mortality than the control during all counting days; hig her dosages had stronger and more rapid effects. A few adults survivin g to 0.5 kGy produced some eggs, but none hatched. For eggs, juveniles , and adults, 0.5-1.5, 1.0-1.5, and 1.5 kGy, respectively, achieved 10 0 % mortality and would meet the probit 9 security standards required for quarantine inspections of fruits after shipping. While the limited survival of juveniles and adults at relatively small dosages did not satisfy the widely accepted probit 9 quarantine security level, it doe s not represent a risk to countries importing produce from Chile, as t hese mites were unable to continue their cycle and reproduce.