I really need some expertise on this ongoing problem since it is not possible to reach the tops of our pecan trees with spray unless we go professional. We moved into a house with 8 very large pecans. I have tried various treatments and know of a couple which you cannot readily find the items needed. We prefer using BT, unless I want a quick kill for personal reasons; but the spraying is always a problem. I learned to hit the walnut caterpillars when they're dumb enough to group late in the day. Someone mentioned spreading Sevin dust around the tree base, but that is not economical these days since you would need to spread enough I suppose to assure their contact .
I am investigating to see if I can use the BT spray in my husband's new pressure sprayer. He says nothing but cleaners, and I say BT can't be worse unless the mixture itself is clogging etc. I can understand that the poisons may be a problem. I suppose it would depend on the inert ingredients used in it. I'm working on that.
Next item is Diatomaceous earth. If it works on snails, would it work on caterpillars? Or does it only work on snails since they are moist and readily sticks to them.? Would the hair on the webworms keep it from getting next to their skin, or does it just not cut them? By the way, does the tent , fall webworms or the walnut caterpillars have an enemy. Since I have experienced the fall webworm once on my neck and once down my back, I can readily see why nothing would eat them. I stomp them just out of the sheer pleasure of knowing that one won't make a Mama. Between the worms and the armadillos, I sometimes understand the movie Caddy Shack. I had to move to Texas to actually learn to detest a living creature. And yes, I had a grub problem in this yard. We are improving, but he still makes his rounds, just doesn't tear up my beds quite as bad. It's always worse when the drought sets in. So disheartening when he pops a full grown Penta. Any help would be appreciated, especially your opinion on the Diatomaceous earth.
The Bt products are your best bet. They will not harm your husband's new pressure sprayer. Just rinse it thoroughly with water after use. The Diatomaceous earth will not do much good on the caterpillars. If you are going to go to the trouble of spraying you just as well use something that is going to get them. Be sure to include a little bit of dishwashing soap, like Ivory, Joy, etc. with the Bt spray so that the spray will penetrate the web. Natural enemies of the web worms and walnut caterpillars include the paper wasps and a few parasites. The trick is to break open the web with a pole so the wasps can get it there and get the worms. I hope this information proves useful.