Fall webworm infests trees and shrubs, but aren’t usually deadly
Q:As I drive down the roads recently, I am seeing the ends of small branches on trees covered over by a webby material, and the leaves inside are all tan and dried up. What is this?
A: Even if it is not officially fall, the fall webworm or hyphantria cunea, is out and about, making unattractive webs over the ends of branches on many trees and occasionally shrubs.
The adult moths emerge in late June to early July and mate. The females lay their eggs on the bottoms of tree and shrub leaves. Favorite choices are apple, cherry, ash, oak, willow and birch, but they will go for a number of other deciduous trees. Eggs hatch in about two weeks.
After the eggs hatch, the kiddies will make a loosely constructed silky web over the ends of a branch. Mommy’s eggs and resulting larvae stay together as a little eating herd. They feed on the leaves inside their little tent, but if they need more leaves to eat, they expand the webbing to uneaten leaves. Occasionally, two webby tents merge together for the super-bag effect.
The larvae are yellowish, hairy caterpillars with tufts of long hairs and black and brown markings on their bodies. When the web is white, the larvae are feeding. Brown or tan webs are usually vacant.
This is a native insect pest and there are over a dozen parasites and predators to limit their fun. More good news: Even though these guys eat leaves, they do not eat the leaf buds for next season.
The average 10-yearold boy knows the trick for getting the low-hanging nests. A stick pushed into the web and twirled around pulls them out. Pesticides don’t penetrate the webbing, so don’t waste time or effort on that. Fall tree leaf eaters usually don’t do much damage. But you may want to remove the webs from small trees that have many.
Q:
I have I had some tomato leaf disease in the past and I read about spraying to prevent this. I have sprayed for two summers and the spray has failed both times, last year and this year. I bought a new fungicide so I know that it is not the problem. This is not making any sense.
A:
Let’s attempt to bring some sense to your problem. You already knocked one possibility off the bad news list. That one is using an old fungicide. Fungicides usually don’t have a “use by” date on them. If you have had the product for three or more years, you might think about a replacement.
The other problem is storing any of your pesticides in the garage or somewhere unheated over the winter. Any pesticides that freeze can separate, and shaking them may not cause them to recombine. You don’t know.
Buying the correct fungicide is critical. All the tomato diseases can be controlled by using a product containing chlorothalonil. If using an organic product, check the Organic Materials Review List online (omri.org) for more information.
Make sure to use a pressurized sprayer and not a hose-end attachment to keep the amount of fungicide and water consistent. Have one sprayer for fungicides and another for weed killers, because there is no guarantee you can completely clean out the
weed killers.
Mix your fungicide fresh before each use, because the mixed product will degrade if left in the sprayer. Read the directions on your product to repeat at correct intervals, which is usually once every seven to 10 days. Shake your sprayer, if possible, before using the mix of water and fungicide. Be sure to spay both tops and bottoms of leaves because the fungus can enter either side of the leaf.
Spray in the late afternoon when the sun is off the plants. Do not spray wet leaves, because this dilutes your application. Spray to the point of runoff to be sure enough fungicide is applied. If you have mixed fungicide left, just spray over the tomatoes again to use it up.
Do not water your tomatoes overhead because this washes off your protection. Reapply after rain, which washes off the fungicide. This year, much of Michigan has gotten rain often, so replacing the fungicide as quickly as possible is necessary.
As soon as you see spots on the lowest leaves, carefully pick them off and destroy them — that may slow the spread of your fungal disease — but keep your spraying schedule.