Friday, May 2, 2014

Webworms and a garden visitor

Webworm caterpillar.
This week-- tomorrow (May 3, 2014)- is the Travis County Inside Austin Gardens Tour.  The AgriLife Extension Demonstration garden is on the tour so our Master Gardener group has been working diligently to get things in top condition (and the garden looks great!).  A group was here on Tuesday and they asked me to come out into the garden to give a quick bug talk.  After we went on a field trip across the street to see a harvester ant colony and a leaf cutting ant colony I headed back to my desk.  Fortunately, a volunteer came in and asked me back outside to see what they found.

Webworm webbing.
In one of the trees, they had discovered webworms (see below for more information on webworms).  Not only were there webworms, but there was a Texas Spiny lizard sitting on top of one of the webs eating the caterpillars.  It was so incredibly cute!

The lizard after its meal.
Webworms are caterpillars that defoliate trees and cause large, unsightly webs on the tips of tree branches.  There are 2-4 generations of webworms that occur each year.  The first generation appears now and the last generation occurs in late fall.  The last generation tends to be the most damaging.

Webworm larvae, or caterpillars, are about an inch long when fully grown.  They are pale green to yellow with tufts of long hairs projecting from their body.  Most people notice webbing that they create on branches.  Webworms feed with in the webbing and use it as protection from predators.  When the caterpillars need new foliage to feed on, hey expand the web.

To manage webworms, try the following:
  • prune eggs masses off before the caterpillars emerge (egg masses are on the underside of leaves and are covered with hairs from the adult moth)
  • prune out small webs when they begin to form in the spring
  • knock webs out of the tree with a stick or a high pressure jet of water; you can also open the webs with a stick or water to allow predators into the web
  • look for products with active ingredients such as Bacillus thuringiensis var. kurstaki, spinosad, azadirachtin
    • even when using a pesticide, you first must open the web to get the pesticide to where the caterpillars are located

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