Chitin and bio-control products show promise in battling pesky nematodes

Last week, I discussed some of the practices to help reduce the numbers of nematodes in your garden.

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This past Tuesday, I was cleaning out my garden. In fact, I was picking the last of the string beans and pulling up the plants. The plant roots were knotted, so there is still a heavy infestation of root-knot nematodes present. In this bed, I had a cover crop of rye that I tilled in the soil in early March. So what is my next step in controlling the nematodes? In this bed, I tilled the bed to expose the nematodes to the sun. This will dry out the nematodes.

In a week, I will till again and then cover the bed in plastic for seven to eight weeks. I will see if the solarization process works. In another bed that had nematodes, I am going to try some of the products that I will discuss in this column.

Some of the products have not been tested by the University of Georgia. The information came from the USDA's Web site for sustainable agriculture.

The first one that I will try is an old product: chitin. Chitin is made by grinding up shrimp and crab shells. There are bacteria and fungi that feed on chitin, so you increase the number of these bacteria and fungi by adding chitin to the soil.

So, how does this work to control nematodes? The outer covering of the nematode is made up of chitin. Therefore, the bacteria and fungi eat the nematodes. The times that I have seen this product work is when it is used at the high rate listed on the product - approximately 15 pounds per 100 square feet. You need to put this product out when you plant in the spring or before mid-summer. Nematodes build up numbers all year, but their numbers are highest in late July and August. So you need to have this product out before this time of the year. Some of the brand names that you can find chitin under is Clandosan and Shrimp Shell meal.

The other products include bio-control bacteria, beneficial nematodes, bio-control fungi, and botanical nematacides. Most of these products have not been tested by the University of Georgia, so I can't tell you how well these products work or if they work at all.

The first group is the bio-control bacteria. There are several bacteria that have shown promise as nematode controls. They are Burkholderia cepacia, Bacillus chitinosporus, and Bacillus thuringiensis. The Burkholderia cepacia bacteria can be found in products called Deny and Blue Circle. Bacillus chitinosporus can be found in Activate, and Bacillus thuringiensis can be found locally in products such as Dipel, or Bt.

Other bio-control is beneficial nematodes and fungi. The Steinernema species of nematodes have shown good control of root-knot nematodes in greenhouse trials. There is no recommendation on the rate that you need to apply them. There are two fungi on the market that can help control nematodes: Myrothecium verrucaria and Paecilomyces lilacinus. They can be found under the brand names of DiTera, MeloCon, and BioAct. You will have to order these products.

The last control type is Botanical Nematacides. These are made from plant materials. Some of the plant materials that are showing promise in controlling nematodes are neem, sesame oil and meal, caraway, fennel, spearmint, oregano, and rosemary. There are no neem oil products on the market that are registered as nematode control products, but neem cake has shown good control of nematodes. Some of the products are Nemastop, Dragonfire, Ontrol, Nemagrad, Neem Cake and Armorex. Again, these products have not been tested by the University of Georgia, and I do not know how well they work.

There are a lot of different materials, practices and controls that you can try in order to get rid of nematodes. But no matter what you use or try, nematodes are hard critters to get rid of.

Columbia County Extension Agent Charles Phillips can be reached at (706) 868-3413 or by e-mail at charlesp@uga.edu. The Extension Web address is www.ugaextension.com/columbia.