Answer: Timing is everything when it comes to controlling Zimmerman Pine Moth. Eggs hatch in late summer (August) into caterpillars that wander across the bark, eventually spending the winter under a flap of bark. In the early spring (April) they emerge and wander again across the bark before tunneling through the bark into the trunk or major branches of Scots and Austrian pine. Through the spring and summer, the caterpillar feeds as a borer, pupates, and then emergesas a moth in late summer.
So, your best chance of management is in the early spring when the caterpillars are present or in late August when they again are present. Usually their movement corresponds with saucer magnolias are in the pink bud ot early bloom stage in the spring or when hydrangea flowers are fully opened in the late summer. At these times the larvae are highly exposed and susceptible to an insecticide spray application. The caterpillars must come into contact with the spray before they enter the bark. Once they enter the tree, it is too late. The insecticides permethrin (Astro) and dimethoate (Cygon) can be used to control the caterpillar by spraying the bark and foliage. Or you can use Bt (bacillus thuringensis) on the caterpillars (sold as Dipel). Best wishes with your trees~
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