Citrus replant problem in Iraq I. Possible role of soil fungi and nematodes

Abstract

The role of soil fungi and nematodes in citrus replant problems was investigated. Several pathogenic and non-pathogenic fungi and the nematodeTylenchulus semipenetrans were isolated in about equal abundance from soils which displayed or did not display replant problems. However, in almost all trees showing evidence of decline, infection by the fungusPhytophthora citrophthora had advanced through the roots until it had reached the tree crown. Fumigation of old citrus soil with methyl bromide greatly increased the growth of sour organe. The application of Nemacure, Benomyl and Ridomil 5G confirmed the important role of pathogenic and non-pathogenic fungi and nematodes in the citrus replant problem. Inoculation of methyl bromide-treated soil with the pathogenic and non-pathogenic fungi separately or in combination further confirmed the previous experiments and also revealed an important role ofP. citrophthora andFusarium solani when replanting citrus in old citrus orchards.