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IPM Message for Cranberry Growers: Apr 29, 2014

April 29, 2014

The Entomology Lab reports: With the warmer weather coming along, winter moth (WM) larvae have been picked up in sweeps in Cranberry land! A grower reported average counts of 10 with a high of 17 larvae.  Larvae measured at 1/16 of an inch (see photo below).  

Consider treating with Intrepid, Avaunt or Delegate given that larvae can be found; they will only grow bigger by eating the tiny buds!  Although the numbers may be below threshold, they will get into buds and may be harder to kill once inside.  The threshold of 18 per sweep set is not a long-standing “tested” number; it is a guideline to help management.  Consider only treating pieces where the higher numbers are found and perhaps at reduced rates of insecticide, and then sweep again.  Possibly, the larvae are from the bog and a spray would stop them, but it is also possible larvae may come in from surrounding blueberries and trees and may continue “ballooning” in, and maybe both.  Another consideration is size of cranberry bud… if the buds are too small, larvae may just die, if buds are bigger (i.e., sanded pieces, early varieties, warm locations) larvae may do well and grow faster. 
WM larvae are definitely out in blueberry.  Larry Dapsis, who works at Barnstable County Extension, has been monitoring blueberries for WM and has found larvae in blueberry buds in Falmouth, Barnstable, Dennis and Wareham.  Russ Norton, Extension Specialist with Barnstable County, also found larvae in apples in Sandwich last week on 4/24.  He scouted organic blueberry in Middleboro on Monday 4/28 and also found larvae in the buds.

Note good spray window Friday through Monday, with a possible frost Monday night.

winter moth larva

Photo courtesy S. Garretson