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Have
You Seen? Asian Woolly Hackberry Aphid: This little pest is easy to spot on hackberry tree leaves because it is coated in a white wax. Also populations are huge by summer's end. Another indication is a sticky substance like maple syrup that drips from leaves. While this honeydew is a great nuisance, tree health is not usually jeopardized. Lacewings and other beneficial insects help control this pest. Unfortunately it is not fast enough for pedestrians and car owners, who complain about the sticky mess. Nearly all trees in the valley are loaded with the Asian woolly hackberry aphid even though it was just discovered in California in 2002. Dodder: This annual plant tangles itself in many crops, ornamentals, native plants and weeds. Dodder has threadlike yellow or orange stems and leaves are absent. Infested plants look like they are covered with orange twine. Intermingled in the stems are clusters of cream colored, bell-shaped flowers. Although dodder is capable of limited photosynthesis, it obtains nearly all of its energy from the host plant. For this reason dodder is considered a parasitic weed. Fall webworms: The fall webworm is one of several tentmaking species. Its tents are formed over the foliage toward the outer portions of the tree. Feeding damage is rarely severe, and the presence of silken tents is its primary effect. Hosts include aspen, birch, cottonwood, elm, fruit and nut trees, liquidambar, maple, mulberry, polar, sycamore, and willow. The mimosa webworm attacks honey locust and mimosa trees. Jumping Oak Gall Wasp: Similar to the Mexican Jumping Bean, oak gall wasps are tiny, shiny, purple-black insects. In spring female adults lay eggs inside the oak leaf. After egg hatch the larva feeds and forms a little structure (gall) to live in. Galls look like sesame seeds and start dropping off leaves in summer, when the larvae start moving around inside. Huge numbers may be seen (and sometimes heard) as they hop an inch or more above ground. Eventually the larva inside quiets down to pupate for the winter. Other gall flies and wasps make colorful star-shaped galls, pink-spined turban galls, reddish cone galls or apple galls on oak twigs and branches, but do not produce the jumping larvae. None of these galls are harmful to the tree. Leafrollers: These caterpillars curl leaves over themselves and tie the foliage together with silken threads. They are then protected from predators as they feed on the tree leaves. Unusually high populations can defoliate trees and plants and cover them with silken threads. They are often seen on aspen, box elder, buckeye, citrus, cottonwood, elm, fruit and nut trees, hawthorn, locust, maple, oak, poplar, rose, and willow. Mites: Mites are common summertime pests found feeding on many fruit trees, vines, berries, vegetables, and ornamental plants. Although related to insects, mites are members of the arachnid class along with spiders and ticks. Spider mites, also called webspinning mites, are the most common. To the naked eye, spider mites look like tiny moving dots; however you can see them easily with a 10x magnifying glass. Spider mites are favored by hot, dusty conditions and are usually first found on trees or plants adjacent to dusty roadways or at margins of gardens. Plants under water stress are also highly susceptible. Mites damage plants by sucking cell contents from leaves. At first leaves are stippled with light colored dots and sometimes turn a bronze color. Eventually leaves turn yellow and drop off. Often leaves, twigs, and fruit are covered with large amount of webbing. Spider mites have many natural enemies that limit populations. Broad-spectrum insecticide treatments for other insect pests frequently cause mite outbreaks. Sprays of water, insecticidal oils, soaps, or miticides can be used for management. Slime Flux: Certain species of bacteria cause a white frothy material to exude from cracks or holes in tree bark. This foamy material appears for only a short time during warm weather and has a pleasant alcoholic or fermented odor. It commonly occurs on elm, oak, and sweet gum (liquidambar) trees, but other species are also susceptible. Wetwood: Affected trees exude a sour or rancid, reddish
or brown fluid. It usually seeps from cracks in the bark or wounds.
Wetwood is caused by several species of bacteria, but yeast organisms
may also be involved. It is particularly common in elm and poplar,
also box elder, hemlock, magnolia, maple, oak and others.
August 14, 2003 |