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2022 Midwest Vegetable Guide

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Insect Management Strategies 70 Midwest Veg Guide 2022 Conservation Biological Control: Conserving natural enemies is one aspect of biological control that can effectively reduce pest populations and damage. This can be accomplished in several ways, but the most important is careful selection of pesticides and reducing the overall number of applications. When selecting an insecticide, consider the impact that application will have on beneficial insects. Bacillus thuringiensis (Bt) products, for example, only have efficacy against the targeted organisms (most often caterpillars). Other products, such as flonicamid, are selective at killing insects with piercing-sucking feeding habits, targeting aphids and plant bugs. Choosing a chemical option that has been approved by the EPA as a Reduced Risk product is another way to minimize the impact on nontarget organisms, including natural enemies and parasitoid, when an application is necessary. Proper Identification Properly identifying pests is the foundation on which a good insect management program is built. If the pest is not properly identified, the chances of selecting the correct control strategies are greatly diminished. Many insects and mites can be correctly identified simply because they are encountered so often. However, it never hurts to back up your knowledge base with some reference materials. Your county Extension office has a number of bulletins available that will help you properly identify insect pests. There also are a number of good books available with color photographs of many of the common insect pests. Most entomologists don't like to admit it, but we often identify unfamiliar insects by comparing them to pictures in a book. For a small fee, samples can be submitted to a local plant and pest diagnostic lab. Beneficial organisms can be important components of an effective insect management program. Being able to distinguish the good insects from the bad insects may help you avoid unnecessary and possibly disruptive pesticide sprays. Some common beneficial organisms all growers should be able to identify include lady beetle larvae and adults, lacewing eggs, larvae and adults, parasitized aphid "mummies", minute pirate bugs, and syrphid fly larvae. In addition to proper identification, it is helpful to know as much as possible about the insect's biology including how to identify the various life stage, location or habitat where each portion of their lifestage occurs and the host range of the pest. Insects with incomplete metamorphosis have juvenile stages — called nymphs — that resemble the adults, except that they are smaller and don't have wings. The feeding behavior is usually the same for nymphs and adults. For example, squash bugs and aphids are insects with incomplete metamorphosis. Insects with complete metamorphosis have a larval stage that is completely different in appearance from the adult. Adult insects never grow, so little beetles don't grow up to be big beetles. For example, caterpillars are the immature (larvae form) of moths and butterflies. Insects who undergo complete metamorphosis also have an intermediate stage, known as a pupa, between the larval and adult stages. For caterpillars this is called a chrysalis or cocoon. Larvae never have wings and are not capable of reproducing. Larvae go through a series of molts (shedding their skins) in order to grow. Larvae and adults frequently, although not always, feed differently and move between plants or plant parts as they develop. In many instances, the immature stage feeds below ground while the mature is found above, or vice versa. Beetle larvae (think Japanese beetles, wireworms, rootworms) feed below ground on plant roots while the adults (again Japanese beetles, click beetles, rootworms) are found above ground feeding on plant foliage. Thrips spend their larval and adult stages above ground, but pupate in the soil. For important insect, mite, and slug pests, it also is helpful to know the overwintering stage, life cycle length, and number of generations per year that can be expected. Again, most of this information can be found in Extension bulletins. Monitoring Vegetable growers must make insect, mite, and slug pest management decisions on an almost daily basis during the growing season. To make the best decisions, it is often useful to have information regarding the current status of a pest's population. This can be accomplished through some sort of sampling or monitoring program. There are several methods to monitor insect populations. Pheromone traps can be used to determine when pests are flying, often times in relation to searching for a mate. This information can be used in several ways. First, catching pests in the trap can alert growers to begin looking for the pest in the field. This can save time because the grower won't be looking for the pest before it is present. Second, pheromone trap catches can be used to time insecticide applications. Third, for some pests, such as corn earworms, the need to spray can be determined from the number of moths caught in the trap. Pheromones are available for many of the moth stages of caterpillar pests of vegetables, and swede midge. Another method for monitoring insects is by scouting fields. Scouting can be formal, such as counting insects on a given number of plants throughout the field, or it can be informal, with the grower walking through the field and looking for the signs and symptoms of insects on the plants. Formal scouting may be more accurate, but the most important thing is for growers to regularly walk their fields looking for insects or insect damage. Most can be monitored just by close inspection of the plants. Others may require the use of equipment such as a sweep net or a beat cloth. Some pests, such as mites, may require the use of a hand lens to see.

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