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How to control Nematodes in a Vegetable Garden

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Written by Aupoet   


 Nematodes can do serious harm to many of the plants grown in home vegetable gardens. These microscopic, soil living, worms, attack plants at their roots. While nematodes do not usually kill their host plant outright, they cause plants to be so weak that they die from other causes and do not bear good crops. There are many ways to control nematodes that do not require dangerous gardening chemicals. Methods that call on the biological control of pests, can be used to control nematodes, prevent nematodes, and kill nematodes.

1.  First determine if nematodes are a problem in the vegetable garden. Some of the plants they will attack are: tomatoes, potatoes, okra, peas, beans, sweet potatoes, and peppers. If there were any of these vegetables in the garden last season that did poorly, were stunted, had yellow leaves, and did not produce well, then nematodes may have been to blame. When the old plants were pulled up at the end of the gardening season, did the roots look swollen with knots and bumps all over them? This is definitely a sign of nematode infestation. The tiny microscopic worms enter the plant roots and feed there, causing the roots to become stunted and lose most of their ability to gather nutrients for the plant. There are soil tests that can be done for nematodes. Check with your local extension service to see about having one done. Nematodes like sandy soil and are much more common in the southeastern US. where the soils do not freeze deeply during the winter.

2.  One of the first and most important defenses against nematodes in the home garden is fall cleanup. Because these plant parasites live in plant roots, a good way to control nematodes, is to pull up and destroy all infected plants especially their roots. Nematode control begins in the fall by doing away with all the roots the worms would overwinter in till spring. Roto-till the garden to find any root pieces left in the soil. Do not place any plant roots into compost piles. Turning the soil several time during the winter will also cut down on the nematode population by exposing the worms and their eggs to the sun and drying them out.

3.  Increasing the level of nematode attacking fungus in the soil is another means to fight these garden pests. Nematodes and their eggs have an outer coating that contains chitin, the same material found in the shells of crabs and shrimp. There are several common types of soil fungus that feed on chitin, so if the population of those fungi are increased, they will attack the nematodes and their eggs. Using a fertilizer or a nematicide made from crab shells or shimp by products, will feed the fungi and cause their populations to rise. Again these products should be applied in the fall and winter prior to planting so the fungus population has time to increase before nematode susceptible plants are set out. Eco Poly 21 and Clandosan are two products to use for this type of nematode control.

4.  There are certain plants that will fight nematodes when used as companion plants, ground covers, or tilled into the soil. Marigolds are well known as a nematode control, but it has been shown in studies that certain varieties are better at the job. The marigold varieties, Single Gold, Nema-gone, Tangerine, and African marigolds have been proven to supress nematode populations especially if they are tilled into the soil as a green cover crop. Other plants that will fight nematodes include: Blackeyed Susan daisy, Indian blanket, and Rape. Use any or all of these plants as companion plants in the vegetable garden, planting them around susceptible crops and then tilling them into the soil at season's end.

5.  Another method used to not only kill nematodes but also to control garden weeds is soil solarization. With this method the soil is heated to lethal levels in order kill nematodes, insects, weeds and their seeds, down to a depth of 8 inches or so. A layer of clear plastic is placed over the soil for a period of a month to 6 weeks during the height of summer and the soil is allowed to bake. First the soil must be tilled well for this method to work, as all large clods and trash must be broken up. If possible till in a layer of chicken manure when working the soil as this will cut the amount of time necessary for solarization in half. Green crop manures will also help especially if they are nematode fighters. Water the treatment area well just before covering it with plastic that is 1 to 4 mm thick and that is UV stabilized. Bury the plastic edges so the wind cannot grab it and make sure the plastic is tight to the ground. You must use clear plastic for soil solarization, black or white will not work. Mid summer is the best time to try soil solarization as a nematode control method because of the long, hot, days. In the deep south this works well with tomato growing as they will not produce during the heat of summer any way. Read my article about growing tomatoes in the south.

6.  Crop rotation is often stressed as a way to control nematodes and plant diseases. This can be difficult in small vegetable gardens and I have found that building up a soil with plenty of organic materials will allow for less attention on crop rotation. If it is possible to rotate the same crops to different areas each year do it, as not only nematodes but soil borne diseases will be cut back. Organic materials that can be used to amend the soil include composts, rotted manures, and leaves. Learn about which crops due well in rotation by visiting my website, growitveg.com, which has all kinds of information on vegetable gardening.

7.  One of the main ways to control nematodes is to plant nematode resistant varieties. Some vegetable varieties that are resistant to nematodes include: The Lima Bean -Nemagreen, Pole Bean -Alabama No. 1, English Pea -Wando, Pepper -Mississippi Nemaheart, Sweetpotatoes -Georgia red, Jasper, Cordner, Southern Delite, and Resisto, Fieldpeas -Mississippi Pinkeye, Zipper Cream, Pinkeye Purple Hull, Mississippi Purple, Mississippi Shipper, Colossus 80, and California Blackeye, Tomatoes -Roma, Celebrity, Early Girl, Beefsteak Super, Red Express, Sweet Chelsea, Sweet Million, Viva Italia, Better Boy, Burpee's Supersteak, Carnival, Lemon Boy, Patio Prize and Sunripe. Look for tomato varieties marked VFN as these are resistant to some tomato diseases and nematodes. If you are trying to grow tomatoes in the south, in zones 8 or 9, read my article about how to grow them.

8.  There are beneficial nematodes that are used to control other soil and garden pests. Some will prey on flea larvae, fly larvae, and beetle grubs. By using biological pest control methods that specifically target the harmful nematodes, beneficial species of them and of other soil living creatures will not be harmed.

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