Express News Article GARDENING, ETC
December 2, 2001
This week's article from the Cooperative Extension office in San Antonio is in response to several phone calls over the last week from concerned homeowners about insects seen on local window screens in high numbers.
If you have little black gnat like bugs all over the outside of your house and screens, raise your hands. Uh-huh, just as I expected... a lot of you. Now, how many of you have a hackberry tree in your yard or your neighbor's yard? Looks like about the same number of hands. Well, there is a correlation. Oh, you can put your hands down now.
The
little black bugs are not a fly or a gnat. They are not dangerous, and contrary
to what you may have felt or heard, they do not bite. The insect is officially
known as the hackberry psyllid (pronounced "SILL-id"). These insects are in
the same insect order (Homoptera) as cicadas, leafhoppers and aphids. Hackberry
psyllids are responsible for the bumps on the hackberry leaves during the summer.
The
hackberry psyllid starts life as an egg laid on young developing hackberry leaves
in the spring. The young psyllid starts feeding on the leaf and the leaf very
quickly develops a little pocket that the small insect crawls inside of. The
pocket then seals over and the immature psyllid spends the rest of the summer
sucking on tree sap safely tucked away inside the little green gall. The feeding
damage is minimal and appears to do very little harm to the tree.
In late summer, the immature psyllid changes from an immature to an adult. In the early to mid fall, the adult psyllid emerges. This is what we are seeing right now. These critters will swarm in the hundreds and thousands and land on almost anything. They have one thing in mind right now: finding a location in which to hibernate through the winter.
If they do come inside your house, they will not cause any damage, other than being a nuisance. They have a piercing sucking mouth. They won't chew holes in clothing or eat food. They only feed on hackberry trees so they won't be a problem on house plants. They have stout little legs. If they land on you it may feel a little prickly, hence the sensation of being bitten. They don't bite and should not be feared.
Unfortunately, there isn't a lot we can do to reduce their numbers. Many times they've already emerged from the leaf galls before the leaves fall off the trees. Raking the leaves probably won't help reduce their numbers either. They are nearly impossible to control in the spring. There is such a short period when they are vulnerable to sprays before being enveloped in the gall that spraying isn't practical as well. There are some natural predators that can help reduce the numbers, such as parasitic wasps and ladybugs. Like all insects, there are cycles in their populations. Right now we just happen to be at a high in their population cycle.
If you have large numbers on the side of the house, you could spray them with a general yard or garden insecticide. But there will probably be just as many tomorrow and they'll be unaffected by the residual sprays. You are probably better off to just hose them off with a garden hose. Spraying under the hackberry trees and around the leaves won't do any good either, as most of them have left that area already. They're all on your window screens!
As the weather becomes cooler, their activity will decrease and hibernation
will set in. But with every warm spell, like Thanksgiving week, for the next
month, we can expect to continue seeing these little rascals.
Excerpts for this article were taken from an article provided by Chuck Otte, Geary County Extension Agent, Kansas State Extension, and edited by Bexar County Extension Agent, Nathan Riggs. For more information, call (210) 467-6575.