Winter Moth chomps its way up the seacoast.

Adult Male

Adult Male

Adult  female

Adult Female

 

 

 

 

 

 

 

Winter Moth are starting to enter NH and have been reportedly seen in ME.

With the arrival of Winter Moth from our southern neighbors we need to talk about them. Winter Moths are hard to control as they are often high up in large trees and they start to feed inside the buds before the trees leaf out. A natural fungus called Bacillus thuringiensis (sold ad BT) will kill them in the early instars; Spinosad or Pyrethroids will kill them any time. Spinosad will kill bees if they get in contact with the chemical before it dries, but is much gentler on them than Pyrethroids. BT will not kill bees. In addition a horticultural oil treatment very late winter can help by killing some of the eggs, but since the eggs are often high up in the tree and laid in bark crevices good control cannot be expected with the oil spray.  Unfortunately Winter Moths balloon back in from surrounding trees so no treatments will be 100% effective. Ballooning is a term used when caterpillars travel in the wind using silken threads like a kite.
Recently I was talking to one of my former colleagues from the Ct Agricultural Experiment Station and he suggested that if would be possible to get good control of this pest with trunk applications at the correct times. The first application would be as the moths hatch around thanksgiving and the females climb up the trees to lay eggs. The second would also be a bark treatment to kill the larvae inside the bud, timed just as the buds swell in the spring.
This approach makes a lot of sense and I shall be trying it soon. The first bark treatment for the adult females would be with a long residual Pyrethroid such as Bifenthrin. The second would be with acephate (usually known as Orthene). This chemical is highly water soluble and will travel quickly through the bark and up to the Winter Moth Larvae. One may worry about Orthene as it has a reputation for being a toxic and broad spectrum pesticide. Broad spectrum means that it kills a wide range of insects including Bees and predators. However being an organophosphate it has a very short life and should be broken down within a few days after application. Because the chemical remains inside the tree there is less chance that it will kill Bees or other insects.
So even though Orthene might be more toxic than some other treatments it may actually be safer than a less toxic pesticide like Spinosad that is sprayed on the foliage.
The good news is that hope for control of winter moth may be on its way in the form of a fly.
See article. http://ag.umass.edu/news-events/highlights/finding-protection-predator

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