Nematodes lay eggs that hatch into small versions of the adult animal. Eggs of potato cyst eelworms can remain dormant inside the cysts, which are the hardened bodies of dead females, for several years in the absence of suitable host plants. When potatoes or tomatoes are planted in infested soil, chemical emanating from the plant roots stimulate the eggs to hatch. Many nematodes will have numerous generations a year and will breed continuously while conditions remain favourable.
Role of nematodes in gardens
From the gardener’s point of view, there are good, bad and neutral nematodes in gardens. Those nematodes that help control certain soil-dwelling pests are welcome. However, the nematodes that feed within plant tissues can be very damaging.
Most nematodes, such as those that feed on bacteria and fungi, have little direct impact on gardens but the vast numbers of nematodes means that they are a significant part of the animal biomass in soil, leaf litter and compost heaps.
Because of the long persistence of potato cyst eelworms eggs, it can become impossible to grow worthwhile crops of potatoes once a damaging infestation has built up in the soil. Phlox eelworm causes stunted swollen shoots with leaves at the shoot tips drastically reduced in width. Narcissus eelworm causes stunted growth and causes the bulbs to rot. Leaf and bud eelworms damage the foliage of a very wide range of plants, causing brown dead patches between the leaf veins. Chrysanthemum, Japanese anemones, Penstemon, foxglove, Buddleja and ferns are frequently damaged.
Free-living nematodes that feed on roots kill the fine root hairs and can cause stunted growth on a wide range of plants. They can also transmit some plant virus diseases, especially of soft fruits, such as strawberry and raspberry.
Other sources of information
Goodey, J.B. (1963) Soil and Freshwater Nematodes. John Wiley & Sons
Perry, R. N. & Moens, M. (2013) Plant Nematology. CABI Publishing
Page text drafted by Andrew Halstead, reviewed by Andrew Salisbury, compiled by Steve Head