Back to top

IPM Message for Cranberry Growers: April 16, 2021

April 16, 2021

Frost Update. As of Thursday April 15, we have accumulated 86 GDD (the threshold for frost to start according to the Dee model, using 44F as base T, is 100 GDD). Also note we reached the long day mark on April 7th. For the most recent reports and photos, go to

Tolerances are as follows (as of Monday April 12);

  1. EB and Howes = at 20F = White Bud Stage
  2. Stevens and Ben Lear = 22F = White Bud Stage
  3. 2nd Gen Hybrids = 22F = White Bud Stage

Upright dieback or Plant Stress.  Following up on the vine stress reported last week (with thanks to Erika Saalau-Rojas, OSC and Frank Caruso, retired UMCS Plant Pathologist).  According to Frank, upright dieback symptoms may show up in spring shortly after pulling off the winter flood, which would correlate with what we have been seeing this year. He recalls seeing a lot of dieback in 1986 and mentioned that infection and symptoms might have been predisposed by other environmental factors such as drought, early cold temperatures in the fall, oxygen deficiency, warm January days followed by cold days. We have certainly seen most if not all of these potentially predisposing conditions during the fall/winter of 2020-21.  So, is what we are seeing truly “upright dieback disease” or some sort of abiotic stress or a combination (in some locations)?  You/We still need to get confirmation of diagnoses and the samples brought into the UMCS diagnostic lab over the past 2 weeks should help to shed some light on what proportion of samples actually have the pathogen (or not).  Leela is anticipating a 2-week turn-around on diagnoses and since fungicides would go out in mid-May, we are still in a good time frame to plan for fungicides, IF they are warranted.  If you see symptoms and have not yet brought in any samples, you should do so as soon as possible so that if you need to apply fungicides, you will know in time for apply once the buds have broken dormancy (usually around mid-May).

  Affected uprights in current year's growth; diseased on left, heathly on right

Affected uprights in current year’s growth; diseased on left, healthy on right

  salt and pepper pattern, typical of upright dieback

Salt and pepper pattern, typical of upright dieback

  bronze, orange discolored uprights more noticeable along equipment track marks

Bronze, orange discolored uprights more noticeable along equipment track marks

Need Contact Hours? We are holding our Pesticide Safety meeting on April 27 and 28, from 8-11 AM (8-10 is for credit).  Please contact Robyn at or see our most recent  (April 14) newsletter for registration information (