alternatives to pesticides - bugs/pests - Elm Leaf Beetle
Actual size: 1/4”
Elm leaf beetles are generally found on the big American, Siberian and Chinese elm trees and on zelkova, occasionally planted in place of elm. In spring, the adults lay eggs on the leaves. When the eggs hatch, the immature beetles eat all the fleshy parts of the leaf, leaving only the skeleton or veins. After a month or so, they are ready to pupate into the cocoon stage and descend to the base of the elm. They are about 1/4” long, and usually yellowish or golden in color with black markings.
Because the pupae are visible on the ground around the tree, you can destroy them by simply smashing them. The elm leaf beetle can produce as many as three generations in the summer, which can seriously weaken the tree. After feeding on plants in your yard during the summer, beetles try to enter your house during the fall for a warm place to winter. However, they do not feed on anything inside and will not damage your home. Sweep them up and dispose of them. If you use a vacuum, dispose of the bag so they cannot escape after the vacuum is stored away, or place the bag in the freezer for several days to kill the beetles.
Bacillus Thuringiensis (Bt) - Check with your nursery for a specific variety of Bt that attacks beetle larvae. Bt is a bacteria used to control certain pest larvae, primarily caterpillars. Bt is not toxic to humans or other mammals but will kill butterfly (“friendly”) caterpillars as well as the problem ones. The bacterium kills larvae by interfering with digestion. Bt lasts on leaf surfaces five to seven days and must be ingested to be effective. There are many strains of Bt commercially available now, including strains for controlling mosquito and beetle larvae.
Wasps - Tachinid flies and chalcid wasps are effective enemies of elm leaf beetles.
Least-toxic chemical control
Horticultural Oils - Horticultural oils are also called summer oils; these are more highly refined than dormant oils, making them appropriate for use on leaves during the growing season. Summer oil can control elm leaf beetle eggs and can be applied in the spring. Consult a nursery to locate a suitable product and follow all precautions. Don’t use horticultural oils when plants are flowering.