Email Apple Pest Message April 3, 2014 Winter Moth Eggs Not Hatching

  Hello fruit growers and all those interested in winter moths,

Winter moth eggs have not started to hatch. They also have not started to turn blue. They turn blue a few days before hatching. Winter moth eggs usually hatch around April 10, though I expect it will be later this year. It all depends on the weather from now on.

Blueberry bushes, apple trees and pear trees should be sprayed with an insecticide when eggs hatch and probably a second time once buds open, but before bloom. When winter moth caterpillars hatch, they wriggled into buds that have just cracked open and feed on the inside of the buds. With blueberries, apples and pears, these are primarily fruit buds. Winter moth caterpillars get inside the flower buds, destroying flowers, which destroys the crop. Landscape trees can be sprayed later, once buds open and the caterpillars are exposed to pesticides.

Winter moth caterpillars are pretty easy to kill with most insecticides. For blueberries, apples and pears I recommend using Imidan, though other insecticides such as Malathion or Sevin work too. An organically approved insecticide, Entrust, works well too.

Several people have asked if the cold winter had any affect on winter moth egg survival. The eggs look just fine and Joe Elkinton from UMass said we need temperatures of -20 F to kill winter moth eggs – so the over wintering survival of eggs is fine.
I’ve attached pictures to show you what I’m checking to see if winter moth eggs have hatched. At URI in November, I wrapped two trees with a tree wrap so female moths would stop at the wrap and lay eggs. This concentrated many eggs in one location so I could find them this spring. Two weeks ago I removed the wrap and circled eggs with a Sharpie. These are the eggs I’m checking for hatching. You will NOT see this on trees unless there was a barrier stopping the female moths.
Please email me if you have questions,


tree banded in Novemberwm eggs circledwinter moth eggs in lichen 3.27.14