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IPM Message for Cranberry Growers: Apr 3, 2020

April 3, 2020

Note from MDAR: All pesticide license exams have been cancelled for the foreseeable future due to the limits on social gatherings. For growers with licenses and need credits for an audit this July, MDAR has extended the time that applicators may obtain their recertification credits until December 31, 2020. MDAR is allowing any outstanding credits required to be taken online, through approved training classes. You can read the statement from MDAR here:


We have a new Special Local Needs herbicide for control of moss.  It is made by FMC and is called Zeus XC.  Applications should go out BEFORE the buds reach cabbagehead stage to minimize injury to the vines.  It is Zone II restricted, so if you want to apply in a Zone II, email me your bog’s address (and GPS coordinates, if you have them).  We are not in the office, so if you leave a message on my phone, I may not get back to you as quickly as an email:  Zeus may control other weeds, such as dodder, and it is legal to use the herbicide to target weeds other than moss.  Please see our March 2020 newsletter for more information.  Most handlers are NOT restricting Zeus but you should double check with your handler before using (Ocean Spray is NOT restricting).


As of March 29, 2020, the GDD based on a base of 44°F was 83.5°F accumulated.  Here are some details shared by Peter. 

  1. The WI model uses a base temperature of 41°F and the Dee Model which we go by uses a base of 44°F.
  2. The WI model does not start counting GDD accumulation until a 13hr day has been experienced—usually this happens around April 7th.
  3. The Dee Model starts counting from January 1st and needs to achieve GDD 100°F to trigger bud monitoring.
  4. We are shy by 16.5°F based on the Dee Model for us to start monitoring
  5. Warm temperatures are predicted for the week starting April 6, especially inland, so GDD could add up quickly.
  6. Current bud status as of Thursday April 2 is red and tight (still dormant) but EB started greening below the buds---so it is the one to watch in the next few days.

Late Water floods are to go out before the vines have lost dormancy and are typically held for 30 days.  Inland areas usually start between April 10-15, Coastal Plymouth is April 15-20 and the Cape is usually April 20 or later.  Bear in mind, these time frames were generated with Early Black and Howes in mind. If you have large-fruited hybrids (and particularly if your farm is inland), you should be out there monitoring progress, so that you get your flood out at the right time.  Conventional Wisdom says that floods should not be held if vines appear stressed coming out of the winter.  Bogs with poor water quality may not be good candidates and any condition that contributes to the loss of carbohydrate reserves can be a bad predictor for LW.

Populations of gypsy moth and winter moth are very low, and the cool weather is slowing development, so early sweeping is not as necessary until into May.  As bogs green up, scale spots may be able to be picked up and assessed. Contact Marty at for more information on scale.

We will be sending out the Chart Book updates by email and snail mail early next week.  We have copies of the 2018-20 Chart Book at the Station.  If you need a copy, please contact Krystal at to arrange a pickup during the Stay-at-Home advisory. Please do not just drop by the Station!  She will arrange a pickup with you. We are working remotely to minimize our contact with others and to protect our health and yours! We appreciate your help in this regard and your understanding!