There are thousands of varieties of nematodes, some beneficial and some harmful. Nematodes have adapted to just about every ecosystem on the planet—they live at high and low elevations, in polar and tropical regions, in fresh water, seawater and on land. In the world of soil-based agriculture, most harmful nematodes fall into the sting, lance or gall types. According to the APS (American Phytopathological Society), nematodes account for an estimated 14% of all worldwide plant losses or nearly $100 billion dollars annually!
Root-knot or gall nematodes are the worst culprits of the group. These nematodes form a gall or bump on the root of the plant and live inside it. Although nematodes are microscopic, the galls they form are often quite large. They damage roots so much that they can no longer provide proper nourishment to the plants. It's really easy to see the damage that's caused by the root-knot nematode, and it costs global agriculture a lot of money because it's very difficult to control.
Nematode Control Methods
Methods of nematode control fall into three broad categories: Cultural practices, chemical control and biological control.
Cultural Methods of Nematode Control
Rotating crops is a good way to control nematodes. You may have a crop that’s highly susceptible to nematodes, and then you rotate that field to other crops that are not susceptible. For example, if you have a field that you've been growing tomatoes in for 2-3 years and you rotate that to pasture grasses for 2-3 years, you will systematically and culturally control the nematodes.
The type of root-knot nematodes that damage tomatoes does not colonize the roots of grasses. When you transfer the field to grasses, you're basically creating an environment where the root-knot nematode no longer has a host. If you remove the host, the population will decrease in the field. This is the opposite of monocropping, where you grow the same crop over and over again, allowing the population of nematodes to become progressively more problematic year after year. Crop rotation is a cultural way of controlling nematodes, and it can work quite well. There are even cover crops which produce chemicals that are toxic to nematodes. However, if you have several types of nematodes in your soil, finding a crop rotation that will starve out all of them can be a bit tricky.
Mechanical methods, such as repeated tilling of fallow soil, may also be useful, but may be difficult to implement on a large scale.
Chemical Control of Nematodes
Chemical controls include fumigants and nervous system toxins. Fumigants have to penetrate a large volume of soil to be effective, and some of them volatize quickly. Large amounts of chemicals are often used, leading to increased risk and expense. Methyl bromide, a broad-spectrum pesticide often used for nematode control, is being phased out under the Clean Air Act. This has led to a search for alternatives.
Nervous system toxins can also provide effective nematode control. Because they are not toxic to plants, these chemicals (carbamates and organophosphates) can be applied after plants are growing and nematode damage is visible. However, since human beings also have nervous systems, any chemical treatments that target the nematode nervous system are a potential danger to humans. These chemicals are extremely toxic to humans and other non-target organisms, but there are alternatives.
Biochemical and Biological Nematode Control
Biochemical and biological controls can be used in conjunction with other controls or on their own. By naturally repelling nematodes and improving plant health, these methods may decrease dependence on chemical controls.
SoilTech Corp has two products that can be used for nematode control: Armorex and Nemastop.
Armorex is a full spectrum soil treatment that can help control soil borne fungi and insects in the soil as well as parasitic nematodes. Made from natural oils, it kills on contact and maintains a repellent action against many soil insects, nematodes and fungi. Armorex is exempt from EPA residue tolerance requirements and there are no re-entry restrictions. Sometimes used in place of methyl bromide, Armorex can be used as a soil pretreatment or during the growing season.
Nemastop is used post-planting to control nematodes and fungi. Composed of organic extracts blended with fatty acids, Nemastop can be used on turfgrass, ornamentals and food crops. It’s non-phytotoxic and also carries no residue tolerance.