By By Steve Strong / area horticulture extension agent
Sept. 17, 2003
Worms can be a good thing, if they happen to be earthworms tilling up your garden beds and making free fertilizer for your plants.
However, the wormy critters folks are dealing with during the late summer tend to be a plant pest rather than a plus.
Fall webworms are a prime example, popping up all over the place on pecans, hickories, persimmons, willows and other trees.
Webworm is an apt name for the caterpillar causing the masses of unsightly, grayish webs stuck to the branch tips of prized ornamental trees and shrubs, and there some good and bad points to mention about this particular pest.
The good news is that the damage caused by webworms is mostly "cosmetic," meaning that it looks yucky, but is not really hurting the plants. Webworms have two to three life cycles during the growing season (funny how you never noticed them until now), and early fall is the last time they will reproduce before spinning cocoons for winter dormancy.
As the last batch of webworms hatches out for the season, they spend five to six weeks forming webs and feeding on vegetation. After that, they form cocoons like other caterpillars in the family Lepidoptera (butterflies and moths), and fall to the ground to pupate in loose mulch or soil.
The bad news is that adult moths (small and white with black specks) can lay 350 to 900 eggs on each lower leaf surface, creating a new batch to hatch for the next life cycle.
The other bad news is that there is not much you can do about them without large, powerful spray equipment to reach every web on the tree. To have any effect, spraying needs to be done early just as the webs are formed.
Biological controls for caterpillars are available, such as thuricide (the same naturally occurring bacterium found in garden dipel dust), in addition to other pesticides, such as Sevin or malathion.
Burning the webs out by setting them on fire is not a good idea, and actually causes much more harm to the trees than the worms do.
Pulling the webs down with a cane pole or other implement is probably the best option, considering that webworm damage is mostly on the surface anyway.
Whatever you try, be careful on that ladder, and for further landscape pest control options, check out the MSU Extension Web site at www.msucares.com.
Another caterpillar pest that causes vast damage to Bermuda and Ryegrass pastures is fall armyworms. Also aptly named for their greenish black and brown camouflage stripes (and for the way they march across a grassy field mowing down everything in their path), armyworms crop up every year by late August or September.
Early control with the previously mentioned pesticides is essential for effective armyworm control because they have the potential to destroy several acres in a short time if left unchecked.
Spray early in the day or late in the afternoon when armyworms are actively feeding, and be aware that they hide so well during daylight hours you may never notice them (the 2-3 inch long worms are easily identified by an upside down white Y-shape in the middle of their black heads).
Hunters with early planted ryegrass food plots will usually realize too late that armyworms have attacked, when the field that sprouted fresh and green just a few days ago is suddenly dead as a doornail. Do not blame your local farm supply for selling you bad seed; if that were the case, it never would have sprouted in the first place.
Instead, be prepared when you plant the field to scout for early armyworm invasions, because right now the weather is perfect for caterpillar attack.
Until the next edition of As The Worm Turns, wear long sleeves when working around shrubbery to protect against saddlebacks and other stinging caterpillars, which have spiny toxic hairs that can almost set your skin on fire.