Sampling highbush blueberries for Rhagoletis mendax (Diptera: Tephritidae) reveals shifting activity timing and cultivar susceptibility.

Abstract

The blueberry maggot, Rhagoletis mendax Curran (Diptera: Tephritidae), is a native pest of blueberries in eastern North America. Invasion by spotted-wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), has caused increased use of insecticides during R. mendax activity resulting in control of both pests, however recent detections of early-season infestation by R. mendax suggests a changing phenology. Monitoring of adult flies over multiple years revealed R. mendax activity shifting approximately 3 wk earlier in the season at times when D. suzukii activity is low. Larval sampling in infested blueberry fields over 11 yr showed a similar changing pattern of activity. Berries collected from a multicultivar planting over 3 yr revealed that R. mendax laid eggs most often in ripening fruit and can even lay eggs in green fruit, indicating risk of infestation before D. suzukii infestation risk. Significantly more R. mendax were detected in later ripening cultivars than earlier cultivars, reflecting overlap between ripening stage and fly activity. When collected pupae were placed in non-overwintering conditions, approximately 1% emerged as adults within the first 57 d, showing that non-diapausing individuals have potential to also extend activity late in the season. The results presented here suggest that R. mendax can adapt to competition from invasive competitors, although the risk of fruit infestation remains highly influenced by overlap between flight activity and berry ripening.