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Soil Nematodes: Good, Bad or Both

January 26, 2024

By Certis Biologicals

Nematodes are well known as the grower’s invisible menace. But what are they, really?

Meet the microscopic worms that live in your soil. Although many growers have a negative association with the word “nematode,” some can be beneficial for the plants they dwell in and around. Many, however, can be detrimental to crop health and yield.

Nematodes are of the large phylum Nematoda, most of which are microscopic (less than 1 mm long) and invisible to the human eye. These tiny creatures are the most numerous multicellular animals on earth. In fact, a single teaspoon of soil can contain hundreds of nematodes of varying species. 

While some nematodes are parasites of plants, insects or vertebrates, many more species are free-living in soil where they carry microbes in their digestive systems and on their surface that help distribute beneficial bacteria and fungi through the soil and roots of plants. Awareness of these different nematode types and their role in your soil can help you understand how they may help or harm your crops and yield, and what you should do about it.

Feeding Habits Of Beneficial Nematodes

Most nematode species occur as free-living organisms naturally in the soil, benefitting soil health and the environment. They help break down organic matter (e.g., a compost pile) and can even control pests both above and below ground.

Free-Living Nematodes: 

  • Bacterivores
  • Fungivores
  •  Omnivores
  • Predators
  • Entomopathogenic nematodes 

Free-living entomopathogenic nematodes are beneficial species, capable of infecting and killing insects. Some strains have been produced at commercial scale for application to the soil, where they either hunt or lie in ambush, ready to attack an insect host. Upon entering the host, these nematodes release symbiotic bacteria that produce insecticidal toxins, killing the insect within 24-48 hours. They then feed and reproduce within the host cadaver until their offspring move on to find a new host, distributing beneficial bacteria and fungi through the soil as they migrate.

These species not only regulate pest organisms in the soil, but they also mineralize nutrients into plant-available forms. They do this by releasing excess ammonium, acting as a food source for other organisms and acting as biocontrol agents by consuming disease-causing organisms.

Beneficial nematodes like these may already exist in your soil. But even if they don’t, you can purchase them, mix with water and spread as groundcover to reap the rewards.

Feeding Habits Of Harmful Nematodes

Unfortunately, not all nematodes are rewarding. There are some species called plant-parasitic nematodes that feed on roots in the soil, resulting in plant damage and related challenges.

Plant-Parasitic Nematodes: 

  • Root knot nematodes
  • Sting nematodes
  • Reniform nematodes
  • Soybean cyst nematodes
  • Lesion nematodes

The root knot nematode is the most serious plant-parasitic nematode problem in the world with global distribution and a wide range of host crops. Harmful nematodes like these feed on root systems with a sharp, needle-like structure called a stylet. Root damage caused by plant-parasitic nematodes reduces a plant’s ability to take up water and nutrients, weakening the plant and increasing its susceptibility to bacterial and fungal diseases and environmental stress.

Many symptoms of feeder infestation can go unnoticed while still causing a negative impact on yield. Symptoms are often misdiagnosed as being caused by nutritional deficiencies or diseases before growers know nematodes are in and around the roots in their fields.

Fight Hidden Threats

Since it can be difficult to detect plant-parasitic nematodes in your fields before noticing their negative effects, preventive measures to manage soil health are an integral part of crop yield protection. A soil test can help determine whether plant-parasitic nematodes are a present threat at time of sampling.

Plant-parasitic nematodes are projected to cause an average global crop yield loss of over 10% annually, which corresponds to well over $100 billion dollars worldwide. If nematodes multiply and grow rampant in your soil, you may face serious economic impact to your bottom line. 

In the past, soil fumigants have been widely used to control harmful nematode populations, but most of these have been phased out due to hazards to beneficial organisms, humans and the environment through off-gassing and soil leaching. NemaClean™, however, is a non-fumigant nematicide that delivers excellent nematode defense at a cost-effective application rate that still allows superior application flexibility to enhance an existing IPM strategy.

Don’t wait until it’s too late for your crops. Take preventive measures to minimize yield losses. When you need flexibility and convenience for every stage of growth, choose NemaClean to manage harmful nematodes in organic production and conventional IPM programs.

Learn more about NemaClean


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