Blight and insects

By John Fulton

[June 09, 2010]  Apple and pear trees are having their problems. There is a large amount of tip dieback in some varieties, and this is probably fire blight. Look for a shepherd's crook at the tip of the affected areas as a clue it is fire blight. Fire blight is a bacterial disease; therefore, there is little chance for you to treat it. The common treatment in commercial operations is streptomycin, but it has to be applied before symptoms appear. Bordeaux mixture can also help prevent the disease. Prune out disease cankers when dormant. This disease cost Illinois its pear industry.

Insects are plentiful this year. I don't think we can blame it on the mild winter, but they have great systems of survival.

One insect of note with the wet weather is the earwig. Earwigs tend to be in high-organic areas, as they feed primarily on dead insects and plant material. However, they can and do eat live plant material such as marigolds, zinnias, strawberries and others. They may be a prime suspect if you notice damage but never see any insects during the day. Control can be obtained with insecticides such as bifenthrin or permethrin.

Leatherwing beetles, or soldier beetles, are now present where linden trees are pollinating. They look like pale lightning bugs but don't have the light. These beetles are elongate, soft-bodied and about one-half-inch long. Colors of soldier beetles vary from yellow to red, with brown or black wings or trim. A common and easily spotted species is the Pennsylvania leatherwing, which is yellow with one large black spot on each wing. Most larvae are carnivorous, feeding on insects in the soil. Larvae overwinter in damp soil and debris or loose bark. The adults are also predators, eating caterpillars, eggs, aphids and other soft-bodied insects. They will alternatively eat nectar and pollen if no insects are around. They do not damage plant foliage. Adults are often found on flowers such as goldenrod, where they lie in wait for prey, feed on pollen and mate. Since soldier beetles are beneficial, it is inadvisable to kill them.

Potato leafhopper populations have exploded in the last week. These are the small, pale green, wedge-shaped insects we often see around lights at night. The main garden crop they affect is -- guess this one -- potatoes. They suck sap and inject a toxin back into the plant. The first sign is a yellow "V" at the tip of the leaf. These areas then turn brown or black. Entire plants or branches can die from these tiny insects. Control with Sevin, bifenthrin or permethrin.

The last insect to discuss is the bagworm. Bagworms are notorious pests of evergreens such as spruce trees. We're about to June 15, the traditional date for control. With the warmer spring, we may run a few days ahead of normal. The idea is to have all the eggs hatched before treatment but not wait until the bagworms are almost mature. For control, the traditional standby has been Sevin, but the Bt products such as Dipel and Thuricide have really taken their share of the market the past several years. The Bt products have several good points, including safety to mammals and toxicity to larger bagworms. Since they are bacteria that affect only the larvae of moths and butterflies, it does take a while for the bacteria to build up to the point where they can kill the bagworm. If you are in doubt about whether you have bagworms, check your trees and shrubs around June 15. You can actually see the small bags as the larvae build them. They become very noticeable at about one-sixteenth of an inch long. Treat bagworms early, since larger ones are more difficult to control.

[By JOHN FULTON, University of Illinois Extension, Logan County]