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IPM Message for Cranberry Growers: May 19, 2016

May 19, 2016

Many growers are picking up gypsy moth larvae; sweep sets easily in the 10’s and 20’s.  The threshold is 4.5 average per sweep set but try not to jump the gun too soon.  We are still early in the season and we haven’t seen any of the early season pests yet, like cranberry weevil and cutworms. 

We had a question on using a 24-48 hour flood for GM control. We do not have any modern data one way or the other.  Dr. Franklin observed that a 24 hr flood around May 29 could be effective unless they are very numerous. He notes that even a 12 hr flood could kill them if they are at least a third grown but if abundant, don't wait until the end of May.  He notes that very small larvae can make a "bubble" around themselves and survive the flood but larger worms will thrash about on the surface and die that way. If you try this, please get counts before and after the flood and let us know (Marty x20 or Hilary x21) how you thought it worked.  

Fungicide applications for upright dieback are best when applied at bud break and/or early bud expansion.  Avoid plant stress; that is one of the best approaches you can do.