First Week of June (plus or minus a week): Gypsy Moth
caterpillars begin to show up on beds, mostly blown in from forested areas though they can also overwinter right on the beds. Their numbers can be fairly numerous in some years, although zero were seen during the entire 2009 season by UMaine Extension’s Cranberry Professional. Add the number of these larvae to any cutworms and humped green fruitworms found when using a thresholds table. This insect is cyclic and in the past has undergone major outbreaks every 9 to 10 years in the northeastern U.S. and Canada. The larva is one of North America’s most devastating forest pests (especially fond of oak and aspen). It has no problem eating cranberry foliage as well. Check for patchy infestations that can be spot-treated, e.g.
along bed edges facing trees that might be infested. Check any previously infested areas. Early detection is key:
larvae consume terminal buds and any new growth that has begun. Some Sweepnet ‘First Dates’:
5/29/00, 5/20/01, 6/13/02, 6/12/06, 6/6/07, 5/16/2013 (central Maine), 5/21/2018 (western Maine) (Average of these = May 30th)