EFFECTS OF METHYL BROMIDE CONCENTRATION, FUMIGATION TIME AND FUMIGATION TEMPERATURE ON MEDITERRANEAN AND ORIENTAL FRUIT FLY (DIPTERA: TEPHRITIDAE) EGG AND LARVAL SURVIVAL

Authors: Armstrong, John; Whitehand, Linda

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2005
Publication Date: 8/1/2005
Citation: Armstrong, J.W., Whitehand, L.C. 2005. Effects of methyl bromide concentration, fumigation time and fumigation temperature on mediterranean and oriental fruit fly (diptera: tephritidae) egg and larval survival. Journal of Economic Entomology. 98:1116-1125.

Interpretive Summary: Methyl bromide (MB) fumigant is used worldwide as a quarantine disinfestation treatment for economically important host commodities before export. Most MB fumigation is done in chambers at ambient temperature around 21ºC (70ºF). The chamber is aerated to remove MB after each fumigation is completed, releasing MB directly into the atmosphere. Because MB has been identified as an ozone-depleting substance capable of affecting stratospheric ozone, USDA developed a research agenda for replacing MB or improving technologies to reduce or essentially eliminate emissions. This manuscript reports research showing that MB concentration or fumigation time needed to control Mediterranean fruit fly and oriental fruit fly can be reduced by increasing the fumigation temperature above ambient (25-30ºC), a treatment method that may be applicable to MB fumigation of other commodities and insect pests. This manuscript, which addresses the USDA research agenda for reducing MB emissions, is important because reducing the fumigant concentration necessary for insect control directly translates into less MB released into the atmosphere during aeration.

Technical Abstract: Reported are the effects of methyl bromide (MB) concentration (16, 32, 48, or 64 g/m^3), fumigation temperature (15, 20, 25, or 30ºC), and fumigation time interactions on the survival of Mediterranean fruit fly, Ceratitis capitata (Wiedemann), and oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), eggs and first and third instars. Increasing the fumigation temperature from 15 to 20ºC or from 20 to 25ºC resulted in a significant reduction in fumigation time required for equivalent egg and larval mortalities at all studied MB concentrations; no further reductions in fumigation time resulted from increasing the temperature from 25 to 30ºC. Thus, the optimum fumigation temperature for Mediterranean and oriental fruit fly eggs and larvae was 25ºC. Conversely, increasing temperature and time allowed for a reduction in MB concentration to obtain equivalent mortality. Reducing MB concentrations required for phytosanitary fumigations would save time and expense, and reduce the amount of MB released into the atmosphere during aeration. Mediterranean fruit fly life stages were less than or equal to oriental fruit fly life stages in MB tolerance. The egg stage was generally more tolerant to MB regardless of concentration. However, at 25ºC eggs and first instars showed similar tolerance for the three highest concentrations, with no significant difference between them. Therefore, eggs alone can be used to obtain MB fumigation efficacy and quarantine security data at fumigation temperatures between 15 and 30ºC for Mediterranean and oriental fruit fly. Also described is a fumigation system constructed to study MB concentration, fumigation time, and fumigation temperature interactions on naked fruit fly eggs and larvae in the laboratory.