Studies on the vertical distribution and seasonal fluctuation of the citrus nematode in Iraq

Abstract

Several surveys in Iraq have shown that the citrus nematode, Tylenchulus semipenetrans Cobb, is widespread in its occurrence and responsible for considerable reduction in yield (Natour et al., 1965 and 1975; Maggenti, 1966; Villardebo, 1969, 1971; AI-Hakim, 1975; Stephan et al., 1977). However, so far there have been no comprehensive studies on the seasonal fluctuations of populations. It is generally recognised that a nematode species causes economic damage when its population density exceeds the particular tolerance level of the crop plant. Moreover, this tolerance level varies between climatic regions. A study was therefore undertaken to examine the effect of several soil and weather factors on the vertical distribution and seasonal fluctuations of the citrus nematode in four different localities in Iraq as a basis for predicting damage and identifying the need for control measures.