The impact of soil environment and time of infection on Meloidogyne incognita, Thielaviopsis basicola and their interaction on cotton

Soil biological, physical and chemical characteristics associated with stunted areas in cotton fields in Arkansas were examined in 2007 to 2009. Affected areas were evident in the same location within cotton fields. Greater soil bulk density and galling severity were associated with affected areas. The impact of soil texture on M. incognita, T. basicola and their interaction was evaluated over three years. Soils were non-infested, infested with M. incognita, T. basicola or both pathogens. Plant development and yield were reduced by the presence of M. incognita and T. basicola. T. basicola damage and reproduction were greater in lower sand content, while M. incognita caused more galling and reproduced better in sandier soils. The influence of temporal separation on M. incognita , T. basicola and their interaction was evaluated. Soil was not infested or infested with M. incognita or T. basicola. Plants were grown in non-infested soils infested soils with one or both pathogens at planting, 10 days after planting (DAP) or 20 DAP or for only 10 or 20 DAP. Soil also was infested with T. basicola or M. incognita at planting, and then replaced with the other pathogen at 10 or 20DAP. The interaction occurred when pathogens were present at the same time in the soil and when the two pathogens were temporally separated. The impact of soil bulk density in cotton, M. incognita and T. basicola was studied. Soils were non-infested, infested with M. incognita or T. basicola or with both pathogens. Plant growth was reduced by M. incognita or T. basicola. The interaction greater reduces plant nodes. Root colonization was reduced at the highest bulk density and increased by the presence of the nematode. T. basicola decreased reproduction of M. incognita in all soil textures, bulk densities and infestation times. The interaction between both pathogens in cotton fields may be impacted by soil factors and environment more than pathogen populations. Soil texture and bulk density had greater impact on T. basicola than on M. incognita. The interaction does not require the concomitant presence of both pathogens.