Outdoor Pest Control - Web worms

I have web worms.......again. Last year my pecan tree was infested with web worms. I sprayed the tree with malathion and that seemed to work. Not so this year. I have sprayed and sprayed and they seem to be immune to the stuff now. I have clipped out the now dead branches and burned them. They are still alive and well in the live regions of my almost dead pecan tree. Also, they have now moved into my redbud tree.

Does anyone have a safe and effective way to rid my trees of these nasty worms?

Web worm eggs and pupae overwinter in cracks and crevices in bark. Pupae also overwinter in soil beneath the tree. Webs can be penetrated with stick and worms knocked out into garbage can for disposal. Or, once webs have been penetrated insecticide can be sprayed inside the protective web. My father always rolled up a piece of newspaper and set it on fire, holding the fiery torch to the webs to burn them out. This can put you at risk and harm the tree. A safer option would be to prune out the nests and put them in the garbage.

The best time to spray insecticide is after eggs hatch and before larvae form webs. Once webs are formed they must be penetrated and insecticide must be sprayed inside web. Dormant oil spray like Volck is effective for smothering overwintering eggs and pupae on trees and plants. The use of the oil spray in early spring if often more effective than insecticide. Webs may be out of reach of sprayer on tall plants!

If you keep all the debris cleaned up around tree and spray dormant oil spray, you can usually get webworm population under control. Spray again with oil when buds start to break. Watch leaves for signs of egg masses under leaves. Once there are signs of web worms, spray with insecticide. If insecticide is not your cup of tea, then use instead a biological control called Bacillus thuringiensis. As with insecticide, open nests and spray inside, then spray the tree and surrounding plants and trees. Or, you can open up webs with a stick and let birds and the weather be natural controls.

You can, however, simply ignore the web worms. Although ugly, they go away. Some years are worse than others. In mature trees, any damage tends not to be permanent.

Hi Zmcjlt,

You asked for something safe to use. Bt aka Bacillus thuringiensis would be the safest organic spray I can think of. Part of the problem with webworms is wasps are a major predator of these pests. The use of chemicals that kill the wasps have resulted in less predators being available. Take a look here.
http://www.dirtdoctor.com/view_question.php?id=96

Newt

Thanks Newt and Twelvepole,

I bought Bt yesterday and am going to give it a shot this evening. The webworms in my neighborhood have been so bad this year they have actually killed a number of trees. My pecan tree is struggling.

We have a number of red wasps. Where would I come across the wasps I need to control these pests? I assume we have them here in TX as we have almost every nasty little bug there is.

Zmcjlt, you are very welcome! I did a google with the terms:
trichogramma wasps + Texas
and found this June 2004 article. I wonder if you are in San Antonio and if they are still doing this.
http://bexar-tx.tamu.edu/HomeHort/F1Column/2004Articles/MAY30.htm

...the continuing saga of the webworm in San Antonio. If you all have been keeping up with this article, we mentioned in the March 21 article that Extension, the City of San Antonio, the Texas Forest Service and Bartlett's Tree Service were working on a project to release microscopic Trichogramma wasps in pecan trees to attack webworm eggs before they hatch. While the results on this study are still pending, there is an important thing that you as readers and pecan tree owners who have been purchasing and releasing the wasps on your own need to know: it is now time to release wasps again to attack the second generation of webworms. Based on what we know about the webworm life cycle, the experts in this program agree that June 21 is approximately the time when new webworm moths will be emerging to lay eggs on pecan trees. Purchasing Trichogramma wasps and releasing them in your pecan trees over the next seven to ten days will afford the best opportunity to affect this next generation. Trichogramma wasps are available from two Texas insectaries: Biofac in Mathis, TX (1-800-233-4914, http://www.biofac.com) and Kunafin in Quemado, TX (1-800-832-1113, www.kunafin.com). They can ship the wasps for delivery within two to three days after the order. The wasps come on little strips as parasitized caterpillar eggs and should be hung in your tree from a limb. Take caution: many species of ants like to remove the eggs from the strips and eat them! To lessen this chance, apply petroleum jelly, tanglefoot or Teflon tape to the wire or string from which the strip is hanging.

This article was written by Nathan Riggs, Extension Agent-IPM with Texas Cooperative Extension in Bexar County.

You should find this helpful too.
http://www.ncera125.ent.msu.edu/GuideTricho.htm

Newt