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2022 Midwest Vegetable Guide

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Nematode Management Strategies 78 Midwest Veg Guide 2022 often do not sufficiently control plant-parasitic nematodes enough to keep their population densities below damage threshold levels. Some manufacturers market products as biological nematicides. See Nematicide Table. Physical Controls Physical nematode control options include using heat, steam, or water (flooding) to reduce nematode population densities. In field situations, these types of controls are often not feasible in the Midwest. However, in glasshouse or poly- house production, growers may use heat or steam to sterilize growing media. Sampling Nematode Populations Plant-parasitic nematodes are microscopic organisms with aggregate (often highly clumped) distributions in fields. As a result, the symptoms their feeding causes often occur in circular or elliptical patterns. If you observe plant symptoms are uniformly distributed, the cause of the problem is typically not nematodes. All sound nematode management programs include rigorous sampling. Since nematodes are microscopic and typically do not always produce noticeable symptoms that indicate their presence, it is necessary to sample to detect nematodes and avoid problems. A great deal of research has gone into sampling nematode populations. Here are three important points: 1. Due to their microscopic nature, the only way to diagnosis a plant-parasitic nematode problem is to collect a soil and/or plant tissue sample(s) and send it to a nematode diagnostic lab for analysis (see State Contact Information table). It is critical to properly identify the nematode's genus or species to provide specific management recommendations. Please refer to any bulletin or other publication devoted to sampling for these organisms for more detailed instructions. 2. When collecting soil samples for plant-parasitic nematodes, the more soil cores you can gather, the better the sample. Collecting roughly 20 soil cores is usually adequate. You can combine and mix these 3. cores. A lab usually only requires you to submit a pint to a quart of soil. You should place nematode samples in plastic bags and close them to retain moisture. Keep the samples out of the sun and heat to ensure that nematodes arrive in good condition for identification at the diagnostic lab. 4. Use different methods for different sample areas. It may be a good idea to separate different areas of the field when sampling. For example, high or low areas of the field or changes in soil types may require different samples.

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