Fall Pest Control And Scott Hininger University of Wyoming Cooperative Extension Service Sheridan County 9/8/2009 Dry Wyoming weather can contribute to severe infestations of aphids and scale insects in ornamental trees and shrubs. Foliar treatments with broad- spectrum insecticides against these pests are often ineffective or provide just temporary relief. In addition, when these insecticides are applied to the foliage, many beneficial insects are killed with the pests. The casualties of these foliar spays include pollinators as well as predators and other natural enemies of pests. As a result, gardens become more prone to pest attacks and need even more frequent insecticide interventions. One answer to this dilemma is a special group of insecticides called “systemics” which offers a viable alternative. These insecticides are taken into a plant through leaves or roots. Insects are killed only when they feed on the treated plants. Such insecticides may be applied to foliage, but there are also granular or drench formulations, which can be applied to the soil near the base of an infested tree or shrub. Compared to foliar sprays, soil applications have obvious ecological advantages because they minimize the negative impact on beneficial pollinators or predators. Other benefits of using a systemic include continuously protected plants throughout most of the growing season without the need for repeat applications, insecticides that are not susceptible to ultraviolet light degradation or “wash off” during watering, and minimized risk of overexposure to applicators. Certain formulations of systemic insecticides claim to provide year-long control against aphids and soft scale insects; however, to be effective, such insecticides must be taken in by the roots, move through the plant’s vascular system and reach the leaves. On average, a systemic insecticide moves up a large tree at a rate of 1 foot per day, so it may take months until it reaches the top branches of a large tree. Do not wait until next summer to protect trees and shrubs. Apply systemics in the early fall, and this will protect trees throughout next growing season. Systemics work best on insects with piercing or sucking mouthparts such as aphids, soft scales and mealybugs. They can also provide suppression of leaf miners, thrips, whiteflies and, in some cases, armored scales and some borers. These insecticides do not affect spider mites. Check the label for the pests that are controlled. With the threat of grasshoppers, again next year, this would be a good defense against them for next year. There are many systemic insecticides available over the counter. Two of the most common include the active ingredients dinotefuran (marketed as Safari) and imidacloprid (marketed as Bayer Advanced Garden Tree and Shrub Insect Control, Merit, Confidor, Marathon® and other brand names). Pesticides are poisonous. Be sure to read and follow directions and safety precautions on labels. Handle them carefully and store in original, labeled containers out of reach of children, pets and livestock. Properly dispose of empty containers immediately, and do not contaminate forage, streams or ponds. One reminder this time of year is to make sure your trees and perennial plants are well watered going into winter. Even with the moisture we have received the last several weeks now is a good opportunity to provide plenty of water under the trees before wintertime. The soil needs to be wet at least 18 inches deep going into winter. Most of the damage (brown needles or leaves) I am seeing particularly on evergreens is probably from spider mites, use a piece of white paper under the leaves or needles to check, they are very small. Regular insecticides do not work use a mitacide or insecticidal soap. The University of Wyoming and the United States Department of Agriculture, Sheridan county Office cooperate. The University is an equal opportunity/affirmative action institution.
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