Protecting Trees from Caterpillars:
(For coming attractions, please scroll down)
The big three of forest consumption: gypsy moth larvae, Eastern tent caterpillars and forest tent caterpillars are again this year munching their way toward a tree near you, if they aren’t already in it. Some tips for taking action:
* All these caterpillars pupate into moths, which don’t feed, by around the end of June to the middle of July. The trees then make new leaves – or try to – and that’s where the trouble really starts because weak trees get exhausted and fall prey to other insects, diseases and climate stress. Thus the most important protection for trees is simply to keep them strong: Water young and newly planted trees regularly; water older and established ones if there is a long dry spell. Mulch to prevent competition from weeds, keeping the mulch away from the trunks so it doesn’t rot bark or lead to insect infestation. And hold off on the strong fertilizer, especially if the trees have been attacked. Whether chemical or organic, food supplements encourage soft growth that’s especially vulnerable to bugs, diseases and (later on) freezes
* While they’re eating, spray with Bt — the younger the caterpillars, the more effective this is, because they have to eat it to die and they don’t die right away. It can also help to band the trees loosely with burlap and apply Tanglefoot or something else sticky. Idea is to keep them from climbing up and down and expanding their range.
* Remove the tents and destroy the occupants. A long stick will usually snag the tents, then you can smoosh them underfoot, drop them into pails of soapy water or – if you’re squeamish – leave them in the center of busy roads. Old timers used to burn ’em out and that’s still a tempting way to go, but it’s very easy to hurt the tree as much as you hurt the caterpillars.
* Later in the summer: Turn off porch lights and garden lights from mid-July to mid- August . Adult moths are attracted to lights from as much as several miles away, and once in your yard will look around for a good place to lay eggs.
* Even later ( next winter in February or March): Use dormant oil sprays in to kill egg masses.
Entomological note: The forest tent caterpillar actually makes resting mats, rather than true tents. Not a saving grace. Kill ’em.