Factors Affecting the Distribution of Plant Feeding Nematodes in Kwazulu-natal

Data from a survey of nematodes associated with sugarcane conducted in South Africa in 1978 (Spaull, 1981) were re-examined in combination with associated soil, climatic and topographic data. The objective was to identify associations between the distribution of the nematodes and soil, climatic and topographic factors in sugarcane fields in KwaZulu-Natal. The procedures used in the survey are summarized as follows. Soil and root samples were collected from 124 fields on a range of soil types in the 11 extension areas of the sugarcane growing regions in KwaZulu-Natal (Figure 1). Nematodes were extracted from the soil and roots, and the numbers of each genus recorded. Soil texture, organic matter content and pH were recorded using conventional methods. Mean annual rainfall, temperature, A-pan evaporation and solar radiation, as well as the altitude of the sites, were obtained from local records. Irrigation water applied to fields was added to the rainfall figures. Distribution and association of the abiotic factors and the nematode genera were studied separately by principal component analysis (PCA) using ADE4 software (Thiolouse et al. (1997). PCA values for the data were projected onto the map of the survey area to study spatial distribution. Association between abiotic factors and nematodes was studied using co-inertia analysis.