(also chrysanthemum leaf nematode; Aphelenchoides ritzemabosi), a parasitic worm of the class Nematoda (roundworm). The chrysanthemum eelworm measures approximately 1 mm in length. It parasitizes the plants of 44 families, mainly the Compositae and especially chrysanthemums. It affects the leaves and buds, causing them to turn brown and dry out. In chrysanthemums the affected areas of leaves are usually bordered by veins and resemble brown triangles. The cycle of development from ovum to adult worm is completed in approximately 14 days; as many as ten generations develop in a summer.
The chrysanthemum eelworm is distributed in the temperate zone. It has been observed throughout Europe, in many cities as well as in rural areas. In the USSR it is found in the European part of the country and in Kazakhstan, Uzbekistan, and Turkmenia. It is also found in the USA, Japan, India, Brazil, and countries of southern Africa. Control measures consist in the selection of healthy mother plants for nurseries, the trimming and destruction of affected leaves, and the treatment of plants with water heated to a temperature of 50°C for ten minutes and water heated to 55°C for five minutes. It is advisable to apply ground sulfur (50 g per sq m) and lime (100 g per sq m) to the soil before planting and to spray the plants twice in late June and July with a 0.2 percent solution of NIUIF mixture.