Fall Webworm & Turfgrass Rust in Ohio – Information and Facts

Strange Phenomena

Near the end of September, things slow down in the Cleveland, OH landscape. School is back in session. If you are a parent, you might find yourself wandering around your yard with nothing going on.

Look up though, and you might see large webs engulfing branches on some of your trees. This can be pretty startling, especially if you are afraid of giant spiders. Not to fear, these are not spiders, they are Fall Webworms.

If you have never came across this before, you might be freaked out. As a result you may have ran inside only to find that you have rust all over your clogs. Now how did that happen? Of course you didn’t step on an old piece of metal in your yard. All you did was walk through the grass. What you encountered was a fungal disease of turfgrass called rust.

These two phenomena can be the strangest pest and disease problems you can come across in the Cleveland, OH landscape. (Spittlebug is pretty weird too. Finding spit all over your plants can be a bit disturbing!) The good news is that it is very rare that any of these will do lethal damage to your plants.

Fall Webworm

Fall webworm is actually a native insect. Populations are kept in check by native carnivores. You can also simply prune them out of the tree. If your tree is small enough I would suggest just cutting them out. If you live in northern Ohio, fall webworm usually doesn’t reproduce fast enough to cause significant injury to a tree. The population can fluctuate and every few years you will see a lot more of them than during previous years.

Controls:

• Chemical controls can be used. If you use a contact insecticide and apply it with a blast of high pressure water you may gain adequate control. Using this method isn’t very efficient though and you end up using more insecticide than you really need.
• A better safer alternative would be to use the bacterial disease Bt, OR Bacillus thuringiensis. It is effective and you spray it on the nest like you would a contact insecticide.
• If you have a large tree it might not be practical to spray it. If you want to protect the tree you can use a systemic insecticide. This is sucked up by the tree’s vascular system and kills the insects as they feed on it.
• Since fall webworm does not cause significant injury to trees in Cleveland, OH you can just remove them by hand, by pruning, or by a blast of water.

Natural Predators

Fall webworm feeds on all kinds of trees. Since it is a native species, all kinds of predators feed on them. Birds, paper wasps, stinkbugs, yellowjackets, parasitic wasps and flies are all predators of the fall webworm.

Most wasps are parasitic and beneficial insects. They help control insect pest populations by laying their eggs in the bodies of pests. The eggs then hatch inside the host and the larvae consumes its flesh. Social wasps like the paper wasp and the yellowjacket are important predators of fall webworm. In August they change from being predatory to sugar feeding that they become a nuisance to humans. That’s when they start dive bombing pop cans at picnics! It is often best to leave stinging insects alone until they stop preying on insect pests that you might be having problems with. You may also want to delay or stop using insecticides on fall webworm to protect off target predators.

Turfgrass Rust

Turfgrass rust is another problem effects your property during the same time as the fall webworm. Rust is a fungal disease of turfgrass. Rust can cause an overall yellowing of your lawn. Its tiny rust colored spores can rub off on your shoes during August and September. Spores are more prevalent when the days are dry and windy; combined with heavy morning dew that sits on the grass blades for an extended period. It gains a foothold in turf when the grass is not growing very much. The fungus easily effects newly seeded lawns that are slow to get established. You most commonly see turfgrass rust on bluegrass and ryegrass lawns. If the grass is healthy and actively growing, the fungus will get cut off each time you mow. In turn it won’t be able to spread its spores on your shoes.

Control

Fungicides can require repeat applications. A quicker control method is to encourage your grass to grow. Water your yard early in the morning. Water deeply and infrequently. Do not water your lawn in the evening. If you do, moisture sits on the grass blades over night Thus encouraging the fungus to grow. If the problem is on going and has become a nuisance, you may want to think about renovating your lawn with newer more disease resistant varieties of turfgrass.