| Blueberry gall midge (Dasineura oxycoccana), European fruit lecanium scale (Parthenolecanium cornii) and Putnam scale (Diaspidiotus ancylus) are potential pests of Vaccinium crops, including blueberry and cranberry. The blueberry gall midge has recently increased in abundance in Michigan blueberries, causing high levels of damage to young green shoot tips. Scale insects have been found in localized areas with erratic population levels. The distribution of these pests in Michigan blueberries, their phenology and the effects of their damage on blueberry plants are unknown, limiting development of management programs. During 2009, surveys were conducted in blueberry farms and nurseries in Michigan to determine the distribution of D. oxycoccana in the state. To determine the phenology of blueberry gall midge, during 2009 and 2010, adult midges in blueberry fields were sampled using emergence traps, yellow sticky traps, and shoot tip dissections. Multiple peaks of damage and larval infestation were found in June and July during shoot growth. Due to the lack of scale-infested fields, monitoring of scale insects was limited to select farms known to be infested with the pest. Insecticide trials on both the blueberry gall midge and Putnam scale were conducted at farm sites and as bioassays in the laboratory. To determine the level of economic impact of blueberry gall midge, in the falls of 2009 and 2010, fruit bud abundance was compared between branched infested shoots and single uninfested shoots. Individual branches of infested shoots were found to have fewer flower buds than uninfested shoots, but overall bud numbers per shoot were similar. |
