How to Kill Nematodes

Nematodes cause widespread plant damage by puncturing cell walls and sucking out their contents, so organic growers should practice crop rotation and use anti-nematode controls like French marigold cultivars Tangerine and Petite Harmony as means of control.

Nematode damage may not be visible to the naked eye, so confirming an infestation requires sending soil samples for testing by a laboratory specialized in nematology. Your local county or state Cooperative Extension offices may be able to recommend commercial laboratories.

Soil Composting

Soil composting has proven itself an effective means of controlling nematode populations, while simultaneously improving soil structure and increasing beneficial microbe populations in the soil. Compost also contains plant-derived nematicidal compounds which have proven extremely successful at suppressing nematode populations.

Many gardeners turn to organic solutions for controlling nematodes, such as composting or crop rotation, as a more natural and straightforward means of control than synthetic methods such as DDT. Though this approach takes more patience and perseverance to implement, organic controls often work effectively against this problem.

Nematodes are microscopic roundworms found in soil that live and attack plant roots. When attacked by these parasites, their pincer-sharp mouthparts pierce through to cause the host plant’s roots to produce galls that restrict water and nutrient movement; ultimately resulting in stunted growth and decreased productivity.

Some species of nematodes are more damaging than others. Nematodes that attack tomato plants form cysts around their roots that prevent them from taking in essential nutrients for growth – known as Meloidogyne incognita root-knot nematode is one of the most serious vegetable nematode pests.

Gardeners looking to reduce nematode populations can add organic matter, like rotted manure, composted yard waste or sawdust to the soil. Such materials contain fungi and bacteria which compete with nematodes for sustenance – starving out their population over time. In addition, organic amendments provide essential nutrients that improve soil conditions.

Other methods for controlling nematodes include planting varieties of vegetables, fruits and flowers that are resistant to them; these crops include corn, millet, grain sorghum, asparagus, chrysanthemums and zinnias. Gardeners may also utilize cover crops like marigolds or sudangrass which contain toxic substances that will reduce nematode populations; black walnut leaves contain an ingredient called juglone that is toxic to nematodes – this compound has also been included as an ingredient in organic products which reduce nematode numbers further.

Nematode Baits

Meloidogyne species nematode infestation can wreak havoc on vegetable crops and ornamental plants alike, leaving many vulnerable. These microscopic roundworms live within plant roots rather than aboveground; making identification challenging. Once in one garden they spread easily by way of tools or boots as well as direct contact between infested plants; similarly Tylenolone tabacum potato cyst nematodes may also prove disastrous to crop production.

Entomopathogenic nematodes are naturally occurring microorganisms that prey upon soil-dwelling insect pests in their larval and pupal stages, providing an effective alternative to chemical insecticides in gardens, lawns, greenhouses, orchards, vineyards and row crop environments.

ARBICO provides an array of nematode products designed to control pests in gardens, lawns, orchards, vineyards, row crops and more. Our Beneficial Nematode Selection Chart will assist in selecting the appropriate nematodes to use against particular pests while our product pages feature instructions, temperature ranges and storage information on each product page.

Not only can organic matter help plants that are beneficial to nematodes, it can also increase predators of these pests such as springtails and carnivorous fungi that can control nematode populations. Furthermore, adding more organic matter can create rich soil which encourages root development further minimizing damage caused by these parasites.

When using nematode baits, it is vital that all instructions and recommended bait materials are strictly followed. Crushed egg shells, sand, grass clippings, castor pomace (a byproduct from producing castor oil) and manure may all serve as suitable materials; the most successful baits contain organic material as well as a high percentage of worms.

Once baits have been prepared, they should be stored in a large Petri dish at room temperature and labeled with information regarding the strain or species being isolated. After an appropriate amount of time has passed, infective juvenile forms will begin emerging from within the baits – these nematodes can then be harvested by taking out of their larger Petri dishes and pouring out into beakers for harvesting.

Nematode Traps

Nematodes are microscopic roundworms found in soil. These microscopic nematodes cause serious crop damage worldwide and four species, known as root knot nematodes, in particular are especially destructive; killing or seriously debilitating plants as they go. Nematodes can also contribute to stunted growth or root rot causing further issues for gardeners.

To effectively kill nematodes, they must first be captured by a nematode-trapping fungus with an attractive carbohydrate-binding protein or lectin that captures and traps them. Such trapping fungi have proven highly successful at killing these pesky bugs.

Fungal parasites attach themselves to the cuticle of nematodes and penetrate it, paralyzing and sucking out their internal contents. Fungus then grows up around them and forms a bulb-shaped structure around it before finally killing off their target and releasing more spores into the soil that continue trapping additional nematodes.

An effective nematode trap can be constructed easily. All it requires is a shallow pan with an open bottom, some cardboard or mesh bag for drainage and some spores for trapping nematodes; either purchased from gardening suppliers or mixed into water in a bowl until it becomes pasty.

Mix the resultant mixture in your container with enough water to fill it, stirring thoroughly as you add more. Apply this solution directly onto the soil where nematodes have taken root; be sure to keep the soil moist and warm until you see an effective change.

Nematode traps can also be created from oyster shell flour, which has proven itself extremely effective against nematodes. Oyster shell flour contains the natural compound juglone which is toxic to nematodes – providing a cheaper alternative than more costly organic products. Black walnut leaves and hulls also contain naturally occurring substances containing juglone which have proven very successful at eliminating root knot nematodes.

Before applying nematodes to your garden, be sure to read and follow the label instructions, selecting the most effective species for your needs. Different nematode varieties target different pests and diseases in different areas; referring to the Beneficial Nematode Application by Crop Chart will help identify which ones would best match with your plantings.


Most gardeners are familiar with plant damage caused by insects and diseases, yet few realize that nematodes are also an ongoing threat for many plants. Nematodes are microscopic worms found living in soil environments which feed off living plant roots by puncturing cell walls with an oral spear-like stylet to cause permanent root damage resulting in weakening or death of these living plant roots. Unfortunately, diagnosing this damage is often challenging due to symptoms like stunted plant growth which could also indicate drought stress, disease or insect infestation among many other issues.

Nematodes are sensitive to heat, making solarization an effective means of control for these pesky bugs. Solarizing requires covering soil with clear (for best results) or black plastic for several weeks or months to trap heat in and heat it to high temperatures – killing not only nematodes but many other soil pests and weed seeds down to 8 inches deep!

This method works best in beds receiving full sun; it won’t be as successful in shaded areas of your garden or those surrounded by trees. Furthermore, it’s essential that both before and after covering it, water should be applied liberally so as to stop any nematodes escaping and reaching deeper soil layers.

After solarization, it is crucial not to till or mix the soil as this could allow nematodes to recolonize. To ensure they have died completely, soil must be immersed in hot water heated to 105 degrees Fahrenheit for three to four hours in order to fully destroy all cysts associated with them and ensure full removal from soil.

Another effective method for eliminating nematodes is planting cover crops like oats, alfalfa or turnips between each year’s vegetable crops to enrich the soil, control weeds and reduce nematode populations while providing natural compost to any organic garden. Marigold flowers have proven particularly successful at combatting root knot nematodes as their petals produce compounds toxic to these nematodes.

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