ISHS Acta Horticulturae 21: I East African Horticultural Symposium
ROOT-KNOT NEMATODES, THEIR INFLUENCE ON THE YIELD COMPONENTS OF PYRETHRUM AND THEIR CONTROL |
| Author: | J.E. Parlevliet |
| Abstract:
Root-knot nematodes are becoming a serious problem in East Africa, although little is known about their distribution and the damage they cause. Whitehead and Kariuki (1960) carried out a survey around Kikuyu, Kenya, at an altitude of 2 200 m to 2 300 m. Many crops were found to be seriously infested with one, two or even three species of Meloidogyne and only a few crops had no root-knot nematodes. Pyrethrum (Chrysanthemum cinerariaefolium Vis.) is widely grown in the highlands of East Africa and almost all of the crop is infested with root-knot nematodes. The multiplication method of division of the rootstock has undoubtedly enhanced this condition. Similar observations were made in the Congo and Delhaye (1968) observed a yield decline, varying with different clones, which he imputed to root-knot nematodes. Pyrethrum in Kenya seems to be almost exclusively infested by Meloidogyne hapla Chitwood and from several identifications, only one plant was found to harbour also Meloidogyne javanica (Treub, 1885; Whitehead and Kariuki, 1960). The crop is grown for the extraction of insecticidal pyrethrins from the flowers which are harvested every two or three weeks during most of the year and then dried. The yield of pyrethrin is assessed on the fresh flower yield, the dry matter content of the flowers and the pyrethrin contents of the dry flowers; flower size has a bearing on the picking costs. | |
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