Tuesday, April 14, 2015

The Spring of Caterpillars

Forest Tent Caterpillar
Photo by: G. McIlveen Jr.
This spring, it sure seems like we're experiencing more caterpillars than we have in the past.  There are two types of caterpillars on trees (seems more of the sightings are on oaks) you may encounter and what to do about them:

Forest Tent Caterpillars.  These guys do not actually make a tent, but they may appear to "wrap" your tree trunks with silk, while they hang out on the inside.  During spring, new growth means tender, juicy food for caterpillars.  While these guys will not damage the overall health of the trees, they may be a nuisance, unsightly, and may congregate in massive amounts on lawn furniture, fences, or other objects.

Oak Leaf Rollers.  It has been several years since these guys have exploded in massive populations, and while this year it isn't a huge explosion, I am getting some calls on them and seeing them drop from trees.  Oak leaf rollers rarely defoliate or even cause any noticeable defoliation of trees, but they are annoying.

Oak Leaf Rollers in oak trees
Photo by: Bart Drees
Oak leaf rollers are usually green in color with a black head. They drop from a single silk strand from trees when they are dislodged.  The silk can cover windows and cars, and when the populations are huge, it can make spending time outdoors unpleasant.

Should you feel the need to manage these caterpillars, they can be treated as any other caterpillar.  Bt and Spinosad are my two favorites.  Bt  is organic and specific to only caterpillars, you will not kill anything else but caterpillars, so be careful around your butterfly host plants.  Spinosad is also organic and may give you a faster knockdown.

I suspect these caterpillars will be around for another week or two, but they will soon die off on their own and treatment really isn't necessary.  Think of them as bluebonnets.  While there are a lot when there are a lot, they won't last long.

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