Blueberry maggot and extreme low temperatures

The Blueberry maggot, Rhagoletis mendax Walsh (Diptera: Tephritidae), is a major pest of blueberry (Vaccinium angustifolium and V. corymbosum) in most blueberry-producing regions of North America. Its geographical distribution is expanding, notably in Quebec, Canada. To document if blueberry maggot can successfully overwinter in northern conditions, the supercooling point of blueberry maggot pupae collected at different times in winter was estimated. The supercooling point of overwintering pupae averaged -22^oC. This result implies that winter temperature is not a limiting factor, because in regions with abundant snow cover, soil temperature rarely fall below -10^oC.

Directive D-02-04 of the Canadian Food and Inspection Agency (CFIA) states that before moving containers that had blueberries coming from blueberry maggot infested areas to non-infested areas, packers must perform one of the three procedures. They must either: 1) clean the containers with hot (85oC) water during two minutes; 2) freeze the containers at 0^oc during 40 days; 3) fumigate the containers. To streamline operations, we tested if blueberry maggot pupae would survive a temperature of -20oC treatment during 0 (control), 2, 4, 7 10 and 15 days. In the control, % emergence of adults ranged from 52 to 80%. In Percentage emergence of adults following treatment of pupae at -20oC treatment during 2, 4, 7 10 and 15 days was 0.