Nematodes are threadlike roundworms that move about in the thin film of moisture surrounding soil particles and root surfaces. The stylet is essentially a hollow spear, like a hypodermic needle, that the nematode uses to puncture cells and feed. The symptoms of nematode infection are commonly those of root impairment, such as growth reduction, increased wilting, mineral deficiency symptoms, decreased winter hardiness, and dieback in perennials. Since many of these symptoms are not necessarily diagnostic of nematode disease, they might be confused for other biotic or abiotic problems. In small plantings, nematode problems initially might escape notice unless there is a similar healthy plant nearby for comparison.
Nematodes contribute to a number of other disease problems as well.
These differences are important because they affect the physiology and growth of the plant in different ways. One basic feature of nematode attack, however, is that nutrients and metabolic activities are diverted from normal, healthy growth and fruit production into sustaining the nematode population and repairing the wounds they cause. This is a chronic problem that continues throughout the growing season. Because of different feeding habits, reproductive potential, and other factors, the damage threshold is different for different species of nematode. The threshold for damage also will vary according to other variables such as plant age, size, nutritional status, moisture stress, and other disease problems.