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IPM Message for Cranberry Growers: July 1, 2022

July 1, 2022

Fruitworm season has begun with hybrids sprayed already.  Check your bog to see if 50% out of bloom is reached to trigger a spray, while waiting a week after 50% out of bloom for Howes. Varieties are wildly different. For example, a Scarlet Knight bed with sandy bog floor was 100% out of bloom this week with all berries whereas a Steven was at 20%. Altacor is the only compound of choice during bloom to protect bees. It is strongly recommended for the first two sprays. Application of Diazinon is out of the question during bloom.

Sparganothis fruitworm, a yellow moth with a brown X on wings, is flying and females are laying eggs that will hatch in 2-3 weeks. A rule of thumb timing for Sparganothis larval infestation is mid to late July; Intrepid and Delegate are the only options. Even if you have cranberry weevil, you must not apply the available pesticides (Actara, Fanfare) during bloom.  It is too late to spray for Golden Casebearer, the tiny yellow beetle that feeds on new growth. Patchy vine injury in affected areas will begin to show up in the first weeks of July.

Putnam scale is at a stunning number of bogs with weak/dead areas appearing. Check the live uprights around suspected areas and look for tiny blips on the woody part of the upright or white spots where the scale has dropped off. Newly established small scales have been found on berries in the calyx and on the berry surface. Look for red dots on the green berry with a white scale in the center. It is too late to treat for the first generation of scale but a new population will appear in mid August and a Diazinon spray could be applied. Young scales in the calyx can look very much like cranberry fruitworm eggs-take note! The scales prefer to settle on the inner surface of the calyx, right where you would expect a fruitworm egg. Honey bees are foraging well on most bogs right now. 

Many growers have already applied 3 fungicide sprays or will doing their third sometime next week.

Grass herbicides, such as Select and the Intensity products, are most effective when applied before the grass flowers.  Especially when weather is hot, use an NIS instead of a COC but always include an adjuvant.  These grass herbicides can be sprayed multiple times and that is a good practice if you have many kinds of grasses out on the bog that are emerging at different times during the season.  Concentrated Callisto sprays for poison ivy can go out anytime now. Try to do it twice (waiting 14 days between applications); efficacy is much better.

During the bogside, we talked about using Cutrine Plus on late water floods.  The label does NOT expressly permit that; we are working with MDAR and the registrant to get clarity on that particular use and will get back to you.