Phenology of the apple maggot (Diptera: Tephritidae) in the Southern Appalachian Mountains.

The apple maggot, Rhagoletis pomonella (Walsh), is an important pest of apples in the Southern Appalachian Mountains. The seasonal phenology of adult flight activity was monitored with baited red sphere traps in eight abandoned apple orchards in the Southern Appalachian Mountains of North Carolina and South Carolina in 2004 and 2005, ranging in elevation from 300 to 853 m. Trap captures showed that at elevations of >/=630 m, the apple maggot was primarly univoltine, with adult activity most intense during a 2-mo period from late June to late August in 2004 and from mid-July to mid-September in 2005. At lower elevation sites in North Carolina and South Carolina (300-328 m elevation), adults were active for a 5- to 6-mo period from late May or early June into November. Trap captures suggested the apple maggot was bivoltine at lower elevation sites. There was also evidence from trap captures of distinct early and late emerging flies from overwintering pupae. A winter simulation study in which pupae from maggot-infested apples collected in July (early emergers) and September (late emergers) were exposed to cold treatments (4 degrees C) ranging from 3 to 52 wk showed that the postdiapause rate was more rapid for early versus late emergers when exposed to a minimum 8-wk cold period. For pupae receiving cold treatments ranging from 8 to 19 wk, early emergers eclosed 257-321 DD before late emergers, but this difference was only 146 DD for pupae receiving a 35-wk cold treatment. Climatic conditions in the Southern Appalachian Mountains, including a relatively long growing season and mild winters, are conducive to a more protracted apple maggot emergence period compared with more northern locations.