Scouting Watch

September 12, 2005

Sod webworm moths were reported last week flying in high numbers on golf courses and lawns. These are light-colored, tan moths about one inch long whose wings fit tight against the body, looking tubelike when sitting on the grass or near lights at night. They have elongated palps that look like a snout sticking out of the front of the head. These moths lay eggs as they fly across the turf in their jerky motion. They typically do not fly higher than your head or more than 30 feet or so before landing. If the drought continues, spray bifenthrin (Talstar), carbaryl (Sevin), halofenozide (Mach 2), spinosad (Conserve), or trichlorfon (Dylox) about 2 weeks after peak moth flight. This will coincide with newly hatched larvae, which eat the grass blades at night. There is a microsporidian, like a bacterial fungus, that is common and kills the larvae. However, it is most effective when it is moist, which is why sod webworms are usually not a problem in irrigated areas or years with timely rainfall. It is this need of moisture by the microsporidian that causes sod webworm damage to be more severe on berms and south-facing slopes.

Galls are numerous on oaks throughout the state. Many of these are leaf galls that look like spiny balls, called hedgehog galls, or shallow cups, called oak spangles. Most oak galls are caused by cynipid wasps, although oak spangles is caused by a gall midge, a tiny fly. Although galls are noticed by clientele, only the gouty oak gall and horned oak gall that are woody and girdle twigs appear to harm the tree. We do not recommend control of any other oak galls. In addition, any control efforts must be made before the gall forms, when the eggs are hatching and before the larvae get established in the plant tissue. For most gall insects, not enough is known about the biology and life cycle to know when egg hatch occurs.

Bagworms have pupated, meaning that insecticide applications will not be effective until next June or July. If you can afford the labor, next year’s infestations can be greatly reduced by hand-picking the bags through the winter and into June before the eggs hatch. About every other bag will be a female bag that contains 300 to 1,000 eggs. Do not drop the bags on the ground because the larvae will hatch out next spring and crawl up the tree or any nearby upright object. They will then balloon to susceptible trees. Destroy the bags by burning or put them in the trash.

Asian longhorned beetle eradication appears to be progressing well. As of early September, no beetles or infested trees have been reported in Illinois by the Illinois Department of Agriculture and the U.S. Animal and Plant Health Inspection Service. This follows the small numbers of four in 2004 and eight in 2003, all in the Ravenswood area of Chicago.

West Nile virus continues to be a problem in Illinois this year; so far, there have been 105 human cases, with two deaths in the state. Hot, dry weather is conducive to the northern house mosquito, Culex pipiens pipiens, the main transmitter of this disease. It prefers to lay its eggs in putrid, stagnant water common during droughts in tree holes, clogged gutters, old tires, tin cans, wading pools, bird baths, and other containers. Clean these out or dump and refill them weekly. Use insect repellent to protect yourself from disease-carrying mosquito bites, particularly in the evening and early morning when this mosquito is most active.