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IPM Message for Cranberry Growers: Jun 29, 2016

June 29, 2016

Growers should be aware that there have been instances of drought stress damage reported in the region.  New, tender growth on cranberry can be very prone to heat and drought damage.  Such damage may be more pronounced this spring because of recent weather conditions of high vine level temperatures, little or no rain, low dew points, and windy conditions.  In addition, saturated soils early in the season from many frost runs may have led to poor root function.  To avoid drought damage, bog soil moisture must be maintained with regular irrigation.  Based on data from tensiometers, State Bog has been irrigated for about an hour every second day during this period. If you think your bog may fall into a catastrophic situation regarding crop loss due to these events, and you have crop insurance, you may want to contact your insurance agent to evaluate your options.

Growers have reported some weevil populations over threshold.  Remember Avaunt is effective against Spring weevils only; do not use now.  Actara is the choice for summer weevil populations.  Actara is Zone II restricted and is Restricted Use.  It is also highly toxic to bees-it is ILLEGAL to use once bloom has begun.

On State Bog, as of yesterday, EB were at 5% out-of-bloom, Demoranvilles were about 18% and Stevens ranged from12-22% o-o-b. Altacor is your best choice for early fruitworm sprays; it does not work well on larger larvae.  First CFW spray for all varieties except Howes is 0-7 days after 50% oob.  The Chart Book recommendation for Howes is 7-9 days after 50% oob, but some are opting to spray when there are swollen pollinated fruit out there (i.e.,  a bit earlier than 7-9 days).  Apply your second treatment 10 days after the first one. Don’t wait to use Altacor later in the season; it is ok to two back-to-back Altacor sprays; you can use Delegate sprays later against second generation.

Our second fungicide went out yesterday, June 28.  We used Proline; only about 0.1 inch of rain fell in the thunderstorm about 5 hours after application. Erika is seeing quite a few cases of Phytophthora. We think this may be due to poor root growth caused by all the frost nights in the spring.  Some flowers are showing symptoms of browning and this could be due to wilt issues and/or stress in combination with Bravo applications. 

At least one grower has reported seeing cranberry flowers with the petals partially fused together after using products containing Clethodim, the active ingredient in herbicides such as Select and Intensity.  The labels prohibit applying these products between hook and fruit set.  A Valent technical representative explained that this restriction is included because fused flowers were observed during product testing, and it was thought that the product might cause flower petals to “stick together” and prevent flowers from opening fully.  During our recent testing at the Cranberry Station, we observed fused flowers after some clethodim applications made during rough neck, BEFORE any flowers were present.  Flower fusing might be caused by internal changes in the cranberry plant, rather than flower petals getting physically “glued” together by the product.  Despite the abnormal looking flowers, the bees were able to pollinate successfully and yield did not appear to be affected but we are still evaluating. 

Poast is another grass herbicide with a related, but different, active ingredient (sethoxydim).  There is no label restriction on applying Poast during hook to fruit set.  It is recommended that Poast be used with crop oil, and grass control is more effective when it is included.  The label states that using Poast with adjuvants at temperature above 90° F (or anytime the temperature exceeds 100° F regardless of the humidity) and relative humidity at or above 60% may result in injury.  Flower petal fusing has not been observed with Poast use.