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.