Yesterday’s warm weather advanced winter moth eggs, turning some eggs blue in some locations. (Winter moth eggs are orange and then turn blue about 2 days before hatching.) In Warwick, RI there are several blue eggs and a few hatched caterpillars. In Kingston, RI about 10% of eggs turned blue. In Cumberland and Little Compton, RI and Hanson, MA, eggs are still orange.
Where you want to protect apples, pears, and blueberries from winter moth caterpillars, I suggest applying an insecticide after the rain on Friday or Saturday or Easter Sunday. If your property is in a cooler location, such as Little Compton, it is still too early to spray.
I think it is best to wait to spray landscape trees until leaves emerge.
From March 4th message about insecticides:
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.