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Cranberry Management Calendar - June


  • All of June: Cranberry Tipworm
  • All of June: Cranberry Weevil (spring brood)
  • All of June: False Armyworm larvae
  • All of June: Blackheaded Fireworm larvae
  • All of June: Cranberry Blossomworm larvae (Average Start Date for Maine = May 29th but most often they begin to appear in early June)
  • All of June: Blunt-nosed Leafhopper (nymphal stages): First seen in 2009 (two locations – outbreak at one location). This is a sucking insect, and most of the feeding is done throughout the nymphal stages, when they are wingless (only the adults have wings). The nymphs need to molt a total of five times before becoming adults, and this development period lasts about one month (essentially all of June and possibly into the early part of July for some Maine locations). In high numbers, leafhoppers will drain the vines significantly (robbing the stems of water and sugar), but most importantly, it is a known carrier of the plant phytoplasm (virus-like pathogen) known as False Blossom, which threatened the entire cranberry industry nationwide in the early 1900s and was so bad in New Jersey that it is said to have nearly ended their cranberry industry there altogether.  Rare pockets of False Blossom are still found in wild bogs on Cape Cod in Massachusetts. You can learn more about this pest on pages 61 to 63 of A.L. Averill & M.M. Sylvia’s book, Cranberry Insects of the Northeast [book can be ordered from the UMass Cranberry Station by clicking here].
  • First Week of June (plus or minus one 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, zero found in 2009. Learn more about gypsy moth [courtesy of UMass]
  • Late June: Spanworms become increasingly abundant

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