Plant eating nematodes, also known as root-knot nematodes, are tiny parasitic roundworms that can cause significant damage to plants. They are soil-dwelling pests that feed on the roots of plants, disrupting the plant’s ability to absorb water and nutrients. This leads to a range of symptoms, including stunted growth, yellowing leaves, wilting, reduced yield or failure to produce fruit or flowers, and the formation of galls or knots on the roots.
Infestations of root-knot nematodes can occur in gardens, crops, and ornamental plants. They are most damaging in warm and humid climates, where they can quickly multiply and spread to other plants. The nematodes are able to infect a wide range of plant species, including vegetables, fruits, flowers, and ornamental plants.
Symptoms
- Stunted plant growth: The knots formed on the roots by the nematodes can prevent the plant from absorbing water and nutrients, leading to stunted growth.
- Yellowing leaves: This can be due to the plant not being able to absorb enough water and nutrients, or from the plant’s energy being redirected to fight the nematodes.
- Wilting or yellowing of leaves, especially in hot weather: When the plant is unable to absorb enough water, it will wilt or the leaves will turn yellow, especially in hot weather when the plant needs more water.
- Reduced yield or failure to produce fruit or flowers: The nematode infestation can weaken the plant, reducing its ability to produce fruit or flowers.
- Galls, or knots, on the roots: The most distinctive symptom of a root-knot nematode infestation is the presence of galls, or knots, on the roots. These knots can be small and round, or large and irregular in shape.
What is a Plant Eating Nematode
- Tiny, round, and worm-like: Root-knot nematodes are small, cylindrical worms that are typically only a few millimeters long.
- Transparent or white in color: They are often transparent or white in color, making them difficult to see with the naked eye.
- Can range in size from 0.5 to 1 millimeter: They can range in size from 0.5 to 1 millimeter, and are usually only visible under a microscope.
- Found in soil near infected plant roots: Root-knot nematodes are found in soil near infected plant roots, where they feed on the plant’s roots and lay their eggs.
- May have a stylet: Some species of root-knot nematodes have a stylet, a sharp mouthpart used to puncture plant cells and feed on the contents.
- May have a gelatinous sheath: Some species of root-knot nematodes are surrounded by a clear, gelatinous sheath that protects them from predators and environmental stresses.
Treating a Plant Eating Nematode Infestation
Root-knot nematodes are difficult to control once established, as they are able to reproduce quickly and are highly mobile in soil. Effective control measures include selecting nematode-resistant plant varieties, rotating crops, and using cultural practices such as crop rotation, soil solarization, and the use of nematicides. Early detection and management is key to reducing the damage caused by root-knot nematodes in a garden or farm.
Physical Control Methods
- Soil Solarization: Soil solarization involves covering the soil with clear plastic for several weeks during the warmest part of the year to raise the soil temperature and kill the nematodes. The plastic should be tightly sealed to the soil to trap heat and moisture. The soil should be left covered for 4 to 6 weeks, or until the soil temperature reaches at least 120°F for several consecutive days. This will kill not only root-knot nematodes, but also other soil-borne pests and pathogens.
- Soil Amendment: Adding organic matter to the soil, such as compost, can help to improve soil structure and reduce the populations of root-knot nematodes. The organic matter can also provide food for beneficial microbes that can suppress root-knot nematodes. The soil should be amended with organic matter before planting to allow time for the organic matter to decompose and the beneficial microbes to establish.
- Sanitation: Removing and destroying infected plant debris can help to reduce the populations of root-knot nematodes in the soil. Infected plant debris should be removed and disposed of in a manner that prevents the nematodes from spreading to other parts of the garden.
Cultural Control Methods
- Crop Rotation: Rotating crops, especially with non-host crops, can help to reduce the populations of root-knot nematodes in the soil. The non-host crops will not be infected by the nematodes and will help to reduce the populations of nematodes in the soil. Crop rotation should be practiced for at least one year before planting the same crop in the same area.
- Resistant Varieties: Selecting nematode-resistant plant varieties can help to reduce the damage caused by root-knot nematodes. These varieties have been bred to be less susceptible to root-knot nematode damage and will grow better in infested soil.
- Companion Planting: Planting companion crops, such as marigolds, can help to suppress root-knot nematodes. Marigolds produce chemicals that are toxic to root-knot nematodes and can help to reduce their populations in the soil.
Chemical Control Methods
- Nematicides: Using nematicides, such as fumigants and soil drenches, can help to control root-knot nematodes. Fumigants, such as methyl bromide and chloropicrin, are applied to the soil before planting to kill the nematodes in the soil. Soil drenches, such as carbofuran and aldicarb, are applied to the soil around the base of the plant to kill the nematodes as they feed on the roots. However, these chemicals can be harmful to the environment and should be used with caution.
- Systemic Insecticides: Some systemic insecticides, such as imidacloprid, can help to control root-knot nematodes by killing the nematodes as they feed on the roots. The insecticide is absorbed by the roots and transported throughout the plant, killing the nematodes as they feed on the roots.
Biological Control Methods
- Beneficial Nematodes: Introducing beneficial nematodes, such as Steinernema and Heterorhabditis, can help to control root-knot nematodes by attacking and killing them. These nematodes are natural predators of root-knot nematodes and can help to reduce their populations in the soil. Beneficial nematodes can be applied to the soil as a suspension or as a dry powder, and should be applied according to the manufacturer’s instructions.
- Microbes: Using microbes, such as bacteria and fungi, can help to suppress root-knot nematodes by competing with them for resources and killing them. Microbes, such as rhizobia and mycorrhizal fungi, can be applied to the soil as a seed treatment or as a soil drench. These microbes can also help to improve soil structure and fertility, leading to healthier plants and reduced damage from root-knot nematodes.