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2022 Midwest Vegetable Guide

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Insect Management Strategies Midwest Veg Guide 2022 71 Familiarizing yourself with the damage they induce can aid in their detection. For example, the stippling of leaves from mites. Alternatively you can shake the plant over a sheet or piece of paper to dislodge the pest. This is effective for mites and thrips. Regular (weekly) monitoring will allow growers to make informed management decisions. In protected environments, yellow sticky cards may serve as a passive monitoring method. The cards should be placed strategically around the crops to intercept pests as they move into the growing space (near ventilation openings) or between crops in the same space. Cards will not control pests but can aid in their detection. They should be checked often (at least weekly) and changed when the surface gets full or is no longer sticky. Determining the Potential for Economic Loss Unfortunately, we do not have economic thresholds for many vegetable insect pests. Whenever possible, we have listed the best thresholds available along with control options in the crop-specific sections of this manual. Although some of these estimates have not been verified by research in each state, they have been derived from scientific research or extensive observations. Growers may wish to adjust these thresholds based on past experience. Extension bulletins also are useful sources of information regarding potential losses from insects. Growers should remember that some crops, such as snap beans and potatoes, can suffer a great deal of defoliation before there is any effect on yield. Sometimes, plants with considerable amounts of insect damage will yield as well as plants that have no insect feeding. If the pest is one that feeds on the marketable portion of the plant, then less damage can be tolerated. Proper Selection of a Pest Control Option In vegetable crops, the selection of a control option during the growing season usually means doing nothing or selecting a pesticide. Although we always encourage growers to read and follow label directions, the one area where the label is not necessarily the best source of information is concerning which insects the insecticide will control. The insecticides recommended in this book for control of various pests are listed because they are legal to use and because they have been found to be effective by the authors. Consider insecticide or biological control agent costs, application costs, relative effectiveness, gain in profits that can be expected from the application, whether it will control other pests, and how it will affect predators, parasites, and pollinators. Growers should refrain from "revenge spraying," that is, spraying after the damage is already done. At that point, spraying is a waste of money and may actually increase pest damage by killing beneficial insects. Evaluation Growers should always evaluate the effectiveness of a pest control action. Inspecting the field a couple of days after an insecticide is applied will help the grower determine the necessity for additional control measures in that field, as well as provide information about the insecticide's effectiveness for future reference. Growers should pay attention to whether the insecticide killed all stages of the pests or if only small larvae or nymphs were killed. They should also notice the effects on other pests in the field and on beneficial insects. Resistance Management It is important to rotate products with different modes of action in order to reduce the potential of insect, mite, and slug populations developing resistance to products with specific modes of action. A pesticide's mode of action is how it affects the metabolic and physiological processes in the pest (in this case, the pests are insects, mites, or slugs). Many product labels contain resistance management information or guidelines that will help vegetable growers determine which products they should rotate with others, including an Insecticide Resistance Action Committee (IRAC) code, that describes the mode of action with a number and/or letter. Try to avoid using products with the same IRAC code repeatedly to conserve its efficacy on pests. Biopesticides derived from fungal and bacterial insect pathogens and live biological control insects can also be deployed against insect pests, further preserving the efficacy of certain insecticides. For more information associated with rotating different modes of action, contact your state or regional extension entomologist.

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