It is still too early to be spraying for winter moth in cranberry, however, we wanted to keep you up to date on WM progress in various spots throughout the region. According to Heather Faubert, University of Rhode Island Extension, winter moth eggs started hatching on Sunday, April 19th in Rhode Island. Many blueberry and apple growers sprayed insecticides over the weekend, protecting flower buds.
As of April 20 (using a base of 40°F starting Jan 1), East Wareham (02538), and Sandwich (02563) had 138 GDD, East Freetown (02717) had 156, Carver (02330) had 129, and South Dennis (02660) had 128. This is still much lower than this time last year (range was 185 to 261 GDD). MA's target for winter moth hatching is 177-239 GDD. To check your area: http://adstest.climate.weather.com/outlook/agriculture/growing-degree-days.
Management: Timing is important because if the newly hatched caterpillars are allowed to crawl inside the expanding buds, they are protected from any insecticide that might be applied. Scouting should be started early (ca. May 1) to catch these populations. Avaunt, Delegate, and Intrepid are the best choices for control of WM on cranberry. If you have a history of WM, you may need to apply a prophylactic spray early in the season. The Action Threshold for WM is 18 average per sweep set.
We do not recommend oils at this time (even though other small fruit growers use them against WM). Marty has not found cranberry to be listed on an oil label (if you know differently, please tell us).
For more information about Winter Moth, see IPM message dated April 9th below.