In Kingston & Warwick, RI, Pawcatuck, CT, and Franklin, MA more than half of monitored eggs have turned blue and have been hatching. In Cumberland, RI and Hanson, MA eggs are a bit behind and just started turning blue over the weekend.
Winter moth caterpillars are pretty easy to kill, provided they are not inside closed buds. Insecticide choices for when caterpillars start to hatch for fruit growers include, but are not limited to, spinosad, Imidan, Sevin, Malathion and synthetic pyrethroids such as Asana. Spinosad products are Delegate, mostly for commercial growers, Entrust for organic growers, and Captain Jack’s Deadbug Brew is formulated for small-scale growing. Adding a dormant oil may be useful for the first spray of any of the listed insecticides.
Once buds are open, B.t. kurstaki products (Bacillus thuringiensis kurstaki) such as DiPel and Biobit work well. For landscape trees, winter moth caterpillars can be controlled once trees leaf out with spinosad (Conserve), B.t. kurstaki (Dipel Pro, Javelin, and others), as well as synthetic pyrethroids such as bifenthrin. B.t. products are a good choice because they kill only caterpillars, but B.t. products break down in sunlight after 3-5 days so may need to be reapplied more frequently.