Infection with cereal cyst nematode is associated with a reduction in grain yield which may be of significant proportions. Thresholds of harmfulness depend on the population density of the nematode and differ among various cultivars and varieties. The weather conditions and soil types are also an important factor, with infections being increased in damp, warm growing seasons. The symptoms of infection include stunting and yellowing of the visible parts of the plant which may give the crop an uneven appearance. The presence of the disease can be established by inspecting the root system of plants and looking for abnormal development. The roots of infested plants develop a tangle of branches and swellings which are white when young but turn dark brown with age. It is the seedlings of cereals that are most readily infected with this nematode and damaged roots are often invaded by soil-borne pathogens such as root and crown rots.