Eelworms and How to Tackle Them

What Are Eelworms?

Eelworms are microscopic nematode worms that live in soil and plant tissue. While some types are actually helpful in the garden, particularly those used to control vine weevil grubs, many others cause serious problems for gardeners. They attack a wide range of common plants and can persist in soil for years.

Chemical nematicides have largely been withdrawn from the home gardening market, though some biological or organic solutions exist in limited availability. Prevention and good garden management remain the primary approaches. Gardening vigilance and prompt action at the first sign of issues are crucial.

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Plants at Risk

Eelworms affect many popular garden plants across different categories:

• Herbaceous perennials such as chrysanthemums, phlox and weigela
• Root vegetables including carrots, onions and potatoes
• Legumes like peas and beans
• Salad crops such as lettuce, tomatoes and cucumbers
• Soft fruits, with strawberries being particularly vulnerable

Different eelworm species target different plants. Potato cyst eelworm, for example, only affects potatoes and tomatoes, while stem and bulb eelworm attacks onions, garlic and some ornamentals. Knowing which type you are dealing with helps when planning control measures.

Your situation may be slightly different. ask a question below ↓ and our editorial team will reply with our advice.

Types of Eelworm and Their Symptoms

Leaf and bud eelworms tend to cause problems from late summer into early autumn. Affected leaves first turn yellow, then darken to brown as the nematodes spread through the leaf veins. The damage often starts in small patches on older, lower leaves before working its way up the plant. In severe cases, whole leaves die and the plant becomes stunted.

Stem and bulb eelworms cause swelling and distortion in stems, bulbs and tubers. Onions may become soft and rotten, while daffodil bulbs develop characteristic yellow streaks. Affected plants often fail to grow properly and may collapse entirely.

Root knot eelworms create small galls or swellings on roots, disrupting the plant's ability to take up water and nutrients. Symptoms above ground include wilting, yellowing and poor growth. Two species of potato cyst eelworm exist, Globodera rostochiensis and Globodera pallida, and both produce tiny cysts on roots that can remain viable in soil for many years. Each requires specific management strategies, making identification worthwhile for persistent vegetable plot problems.

Prevention and Control

Given limited chemical control options, emphasis should be on preventing infestations and controlling spread through integrated pest management:

• Buy plants and seeds from reputable suppliers, checking for signs of damage before purchase
• Practice crop rotation, leaving at least four years before growing susceptible crops in the same spot
• Remove and destroy affected plants promptly by burning or placing in household waste, not the compost heap
• Clean tools, boots and equipment after working with infected soil
• Avoid moving soil from affected areas to clean parts of the garden
• Incorporate organic amendments like composted manure to improve soil health and resilience

For potato cyst eelworm, resistant varieties can help. Seed potato packaging often indicates resistance ratings, and the AHDB publishes current data on variety resistance worth consulting when choosing what to grow.

Some gardeners use the beneficial nematode Phasmarhabditis hermaphrodita to control slugs, but this will not affect plant parasitic eelworms. The two groups are quite different despite sharing the nematode classification.

Fallowing affected ground for several years can reduce eelworm populations, though this is rarely practical in smaller gardens. Growing non host plants in rotation is usually more achievable. Tagetes, commonly known as French marigolds, are sometimes grown as a green manure to suppress root knot eelworm species, though research on effectiveness remains mixed and results vary considerably.

The RHS advisory service offers identification help and should be considered an early step rather than a last resort. For allotment holders or those facing persistent problems, soil testing through agricultural laboratories can identify which species are present and guide targeted management decisions.

The Next Step

Now that you have read through the advice above, you might want to put it into practice. Our Treatment Guide lets you enter the type of pest and where it is causing problems to get a tailored removal guide. Covers both home remedies and shop-bought treatments. Try it now →