You may have had problems with Root Knot Nematodes before. They cause stunted growth, yellowing and wilting during the day with recovery during the night. The crops that nematodes prefer are bean,cantaloupe, corn, carrot, eggplant, okra, onion, pea, pepper, pumpkin, squash, sweet potato, tomato, watermelon, and of course weeds.
Root Knot Nematodes are microscopic worms that live in the soil and feed on the roots of your crops. The Nematode got its name because it’s feeding cycle causes the knots or galls to form on plants. Root knot nematodes come from the genus Meloidogyne, but there is also another strain M. incognita which is known as the southern root knot Nematode.
Life Cycle – Freshly hatched larvae move through the upper 2 feet of soil until each one find a root and penetrates it. It then becomes sedentary. Glandular secretions injected from the larvae into the root cause the surrounding cells to enlarge and form a gall or root knot. The nematode feeds on this. The males are threadlike and the females are pear shaped and whitish. The female deposits 300 to 3,000 eggs in a yellowish brown gelatinous mass. Larvae exit into the soil when the infected root cracks or decays, then the cycle starts again. In the south we have 10 generations.
What Do I Do if I Have Nematodes?
Plant Resistant Varieties– When searching the seed catalogues look for the descriptor N=Root Knot Resistant. There are varieties that are resistant to these little scarps.
Crop Rotation– Rotating your crops is always suggested. If you have had a problem with nematodes then you need to pay even closer attention to detail and plant crops for the next two years in the area to rid your soil of nematodes. Use crops that are non host crops and are known to lower root knot nematode numbers. Use crops such as broccoli, cauliflower, grain sorghum or millet and rye. White and black mustard are said to be a deterrent of the Nematodes. The crops work particularly well if grown for 2 years successively. Another approach is planting french marigolds, such as Tangerine, Petite Harmony or Petite Gold on 7 inch centers Do not use hybrids as they increase the number of nematodes. You must also keep the marigold patch weed free as the nematodes can reproduce and survive on weeds.
Solarization – Take a 2 to 4 mil piece of plastic. Wet the soil to be covered well and tuck in the edges with soil. You will need to leave it in place for 2 months. After you remove the plastic do not till the solarized soil or you will disturb weed seeds and nematodes from lower layers of soil.
Avoid Spreading Disease – Nematodes only move about 3 or 4 feet each year on their own a year. The way that they are spread is by tools, shoes, diseased plants. Make sure that when you pull up diseased plants you burn them or throw them out in the trash. Be careful not to move dirt from a diseased area into a clean area. Make sure to wash your tools with a 10% bleach solution (one part bleach to 9 parts water) after you have used them in an infected area.
Use Cedar Chips for Mulch – Using cedar chips for mulch in an infected area help for many reasons. First, it helps by keeping the spread of the nematodes down from muddy shoes. Secondly, the microorganisms that help to break down the carbon products such as mulch can get rid of nematodes. When you have a pile of mulch there are many organisms that take turns in decomposing it. Each species of population starts out in high numbers and takes over in population, their numbers explode an then subside, each species having it’s turn It turns out that there are nematode destroying fungi that run late in the dominating cycle,and there is still energy left since cedar breaks down relatively slowly thus there is energy to destroy the nematodes.
Bio-Rationales – If you really need to clean up a small area you can use these two products,
Azadirachtin – This is from the two active ingredients in the neem tree seeds.
Myrothecium verrucaria – this is a mixture of the killed fungus, Myrothecium verrucaria, and the liquid in which the fungus was grown. The dead fungus kills nematodes.