Texas A&M is my "go to" resource for gardening problems. Here is a link to information provided about this pest. http://aggie-horticulture.tamu.edu/newsletters/hortupdate/hortupdate_archives/2007/sep07/Bagworms.html
In addition, the Dallas Morning News had a local article about it.
Readers of my blog posts know that my philosophy is to make gardening easy by using native plantings in the landscape that are hardy and need little water. We typically don't use herbicides and pesticides (exception - fire ants). I firmly believe in survival of the fittest. However, these trees have done well in my yard up to now, and trees typically add to property value. We are truly torn between letting the bagworms take them out or trying to save them. We discussed and debated the issue and finally elected to try and save them this season. Here are some photos of our very serious problem.
My son and I fought the first battle by handpicking as many of the beasts as possible on Day 1. After handpicking them, I mowed as close to the ground as possible to maim and kill as many as I could that were still on the ground.
HOW DARE THEM CLIMB UP MY TREE!!
We got a bucketful of the nasty critters.
Day 2 after discovery - my husband sprayed the trees with an organic pesticide. It had no effect at all.
Note his protective gear - for eyes, nose, mouth, and skin. Whenever you spray with pesticides (or herbicides) you cover yourself. Do this even if you are using "organic" products.
Day 3- he sprayed the trees with the traditional pesticide. This had a better net effect - there were some kills - however, on Day 4 when we went out and checked, we concluded at least 75% SURVIVED!!
Too bad neither spray seemed to work.
Now what? I went out this morning (Day 4) and picked more off the trees, but clearly it isn't working. I'm keeping the trees watered - hopefully they will be able to fight back but according to the articles we've read, bagworms are a true killer when they invade and it is difficult to keep them from killing the host plants. In addition, although they haven't attacked my pine trees yet - it is entirely possible that they will according to articles I've read. We started looking at the bald cypress trees planted in the neighborhood - and noticed that ALL of them have bagworms hanging in them now. They are in varying states of distress and it will only get worse. I hate to say it but if we can't pull them through this season, I may cut them down and never replant them as long as I live in North Texas. They are a beautiful tree but this is a serious problem.
DISCLAIMER: MY REVIEW OF THE PRODUCTS MENTIONED ABOVE ARE UNIQUE TO MY EXPERIENCE AND MAY NOT REFLECT YOUR EXPERIENCE WITH THE PRODUCTS.