Abstract

Root-knot nematodes are the most economically important group of plant parasitic nematodes. They are unevenly distributed in the soil making blanket nematicide applications uneconomic. Soil edaphic factors have been reported to be related to nematode distribution and hence can indicate nematode distribution in the soil. This study seeks to find out if the relationship of soil edaphic factors and nematode distributions can be used effectively to manage nematodes. Two year studies were carried out in 2011 and 2012. In this study, 3.3 ha fields were divided into 60 plots to determine factors that have an effect on nematode distribution and tobacco growth. Results in the first year indicated that there was a significant weak negative linear correlation between root-knot nematode populations and electrical conductivity(r = -0.298: p= 0.042). In the second year, more parameter were evaluated. Results indicated that there was a significant weak negative linear correlation between root-knot nematodes and electrical conductivity (r = -0.32; p =0.015), plant height and nematode populations (r =0.19; p= 0.18), plant height and percent clay (r =0.245; p= 0.059) and electrical conductivity and percent silt (r =0.22; p= 0.11). In some studies, electrical conductivity was recommended for use as a quick indicator of nematode distribution. In this study the weak correlations shows that it cannot be reliably used. It was noted that soils close by usually have little variation in texture and hence geo-mapping of nematodes is not feasible in small fields.

Key words: Electrical conductivity (EC), root knot nematodes, spatial distribution, geo-mapping.