Blueberry gall midge (Dasineura oxycoccana), its biology and economic impact in Michigan blueberries

Blueberry gall midge (Dasineura oxycoccana) is a potential pest of Vaccinium crops, including blueberry and cranberry. This cecidomyiid species has recently increased in abundance in Michigan blueberries, causing high levels of damage to young green shoot tips. Feeding by larvae induces branching in damaged shoots. The distribution of D. oxycoccana in Michigan blueberries, its phenology and the effects of its damage on fruit yield and bud set are yet unknown, limiting development of a management program. During 2009, surveys in blueberry farms and nurseries throughout Michigan found D. oxycoccana at nearly all locations. To determine the phenology of blueberry gall midge, during 2009 and 2010, we sampled the number of larvae and adult midges in blueberry fields using emergence traps, yellow sticky traps, and shoot tip dissection, revealing multiple peaks of damage and larval infestation in June and July during shoot growth.To determine the level of economic impact of this insect, in the fall of 2009, fruit bud abundance was compared between branched infested and single uninfested shoots. Individual branches of infested shoots were found to have fewer fruit buds than uninfested shoots, but overall bud numbers were similar. We will review the current information on the biology and management of blueberry gall midge in Michigan blueberries.