Influence of Soil Bulk Density On the Interaction Between Meloidogyne incognita and Thielaviopsis basicola On Cotton

Meloidogyne incognita and Thielaviopsis basicola are both important cotton pathogens. In addition, these pathogens may interact synergistically increasing disease losses. Disease development for each of these pathogens is influenced by environment. Warm soil temperatures and sandy soils favor nematode damage, whereas cool soil temperatures and fine soil texture increase black root rot severity. Co-infection expands the temperature ranges at which both pathogens are able to cause plant damage. The objective of this research was to evaluate the impact of soil texture on each pathogen and their interaction and pathogen survival. Five soils from Arkansas; one soil from Crittenden county (52% sand) and four soils from Ashley county (39%, 50%, 68% and 78% of sand), with long histories of cotton monoculture were used. Soils were pasteurized at 60ºC for 30 minutes. Six treatments were used: 1) noninfested control; 2) M. incognita - 4 eggs/cc soil; 3) M. incognita - 8 eggs/cc soil; 4) T. basicola – 20 chlamydospores chains/g soil; 5) M. incognita - 4 eggs/cc soil T. basicola – 20 chlamydospores chains/g soil; and 6) M. incognita - 8 eggs/cc soil T. basicola – 20