Leaf and bud eelworm

A widely distributed problem that can damage leaves, stems and other above ground plant parts. Leaf and bud eelworm can attack a wide range of plants, in gardens they commonly cause severe damage to chrysanthemums.

Leaf and bud eelworm damage

Leaf and bud eelworm damage

Quick facts

Common name: Leaf and bud eelworm or foliar nematode/roundworm
Latin names: Aphelenchoides ritzemabosi and A. fragariae
Plants affected: Very wide host range including chrysanthemums, ferns, lilies, violets, begonias, strawberries etc.
Main symptoms: Characteristic interveinal yellow, brown and black blotches
Caused by: Plant parasitic nematode
Timing: Summer to autumn

What is leaf and bud eelworm?

Eelworms belong to the phylum Nematoda and are also known as nematodes or roundworms. The Nematoda is a very diverse phylum of animals, there are more than 25 000 described species, and they are found in almost every habitat. Most nematodes are beneficial because they break down and recycle organic material in soil, marine and fresh water ecosystems.

Leaf and bud eelworms are plant-parasitic nematodes, they are detrimental to plant health as they feeding on and damage plant cells. They are microscopic (0.4-1.2 mm), slender and worm-like with unsegmented bodies and a stylet or mouth spear. The stylet is used to puncture plant cells, inject digestive juices and to ingest plant fluids.

They are migratory endoparasites which means they can move into, through, and out of their host tissue. Their movement and feeding causes cell damage or death and the affected plant will show symptoms of distortion. Moisture is essential for their survival. Adults needs a film of water to migrate within the soil but also on the stems and leaves of their host. 

They have a short lifecycle of between 11 to 14 days at 13°C to 23°C. Adults overwinter in dormant buds, seeds and dry plant parts until favourable conditions arise in spring. Populations thrive in warm, humid conditions. They cannot survive in the soil for more than three months without a host but can multiply in plant tissue at -2°C.

Symptoms

Symptoms can vary depending on the eelworm and its host plant/s;

The leaf and bud eelworm Aphelchoides ritzemabosi on chrysanthemums

Growth is stunted due to eelworms feeding on buds. Extreme damage can cause growing points to blacken and die. Stems are dwarfed with a bushy appearance. Leaves appear distorted and deformed with interveinal yellowed blotches turning brown then black. With time leaves shrivel, die and hang down. Eventually flower buds will be infected producing deformed, undersized flowers.

The leaf and bud eelworm Aphelenchoides fragariae on strawberries and ferns

First symptoms are abnormal growth with stunted and deformed buds, leaves and flowers. Twisting and puckering of leaves, undersized leaves with crinkled edges, and tight clustering of crowns are all signs of infestation. Leaf stalks become reddened and stunted, while flower stalks begin to drop flowers. Heavily infested plants do not produce fruit.

On ferns, leaf blotches occur in stripes since their movement seems to be delimited by veins.

On flowering plants such as chrysanthemums and strawberries the symptoms on the flowers appear as water soaked patches which later turn brown.

Control

Chemical control

There are no pesticides available to home gardeners which will control leaf and bud eelworms.

Non-chemical control

Cultural methods can be used to lower infestation and minimize damage.

Good garden hygiene

To manage and restrict spread remove and burn all infected plant material and control weeds which could be potential hosts for the eelworms. Thoroughly clean contaminated gardening equipment and muddy shoes. See disposal of diseased material for more details. Where possible use plant and propagation material certified as nematode free, especially if you have a big collection of a susceptible plant.

Avoid splashing water on leaves

The mobility of eelworms on the surface of plants depends on the presence of a water film while the movement of water through irrigation and rain can disperse nematodes between plants. Avoiding overhead forms of irrigation such as sprinklers helps limit wetting of the leaves.

Cultivar resistance

Resistance is only known in some chrysanthemum varieties such as Amy Shoesmith, Delightful, Orange Beauty and Orange Peach Blossom. Eelworms will invade these cultivars but females produce few eggs and juveniles usually fail to mature. In time the nematode population will fall to insignificant numbers.


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