Soil Texture Influence on Meloidogyne incognita and Thielaviopsis basicola and Their Interaction on Cotton

Microplots were used to evaluate the impact of soil texture on Meloidogyne incognita, Thielaviopsis basicola, and their interaction on cotton. A native silt loam soil (48% sand) and four different artificial soil textures produced by mixing native soil with sand (53, 70, 74, and 87% sand) were studied. Each soil texture was infested with 0, 4, or 8 M. incognita eggs and 0 or 20 T. basicola chlamydospore chains per gram of soil in a factorial treatment arrangement. Plots were watered when soil moisture fell below -10 joules/kg for the first 21 days and -30 joules/kg from 22 days to harvest. Plant growth was suppressed early in the season and midseason by T. basicola. M. incognita suppressed plant growth and delayed plant development late in the season across all soil textures. Cotton yield was lower in the presence of either T. basicola or M. incognita. An interaction between M. incognita and T. basicola, which decreased plant growth and yield, occurred in 2006 when neither pathogen caused substantial plant damage. Plant growth, development, and yield were lowest in soils with >74% sand. Root colonization by T. basicola and fungal reproduction and survival decreased in soil having 87% sand. M. incognita generally caused more galling and reproduction in soils as sand content increased. Root galling severity and M. incognita reproduction were suppressed by the presence of T. basicola in soil at sand contents lower than 87%. Soil texture had a greater impact on T. basicola than on M. incognita in this study.