Now is the time to be looking (and spraying) for winter moth larvae out on the bog! Advanced bogs, hybrid cultivars, and sanded bogs will be warmer and more likely to have growth that is appealing to WM now. These bogs will likely need to be sprayed this week. Later varieties and colder areas will likely need applications next week.
Management: Insecticides sprays timed to coincide with egg hatch are the most effective way of controlling this pest. The 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. Populations may re-occur as larvae can balloon in. 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.
Organic growers can use Entrust (spinosad), or one of the Neem products such as AzaDirect, Neemix, or Ecozin in place of the insecticides listed in the table above. Products that contain B.t., may also be effective but depend on the caterpillars ingesting enough product to be effective.
Check our Winter Moth fact sheet and information from April 8, 2015:
For current regional updates on the UMass Landscape message: