IMPACT OF SOIL TEXTURE ON THE REPRODUCTIVE AND DAMAGE POTENTIALS OF ROTYLENCHULUS-RENIFORMIS AND MELOIDOGYNE-INCOGNITA ON COTTON

The effects of soil type and initial inoculum density (Pi) on the repr oductive and damage potentials of Meloidogyne incognita and Rotylenchu lus reniformis on cotton were evaluated in microplot experiments from 1991 to 1993. The equilibrium nematode population density for R. renif ormis on cotton was much greater than that of M. incognita, indicating that cotton is a better host for R. reniformis than M. incognita. Rep roduction of M. incognita was greater in coarse-textured soils than in fine-textured soils, whereas R. reniformis reproduction was greatest in a Portsmouth loamy sand with intermediate percentages of clay plus silt. Population densities of M. incognita were inversely related to t he percentage of silt and clay, but R. reniformis was favored by moder ate levels of clay plus silt (ca. 28%). Both M. incognita races 3 and 4 and R. reniformis effected suppression of seed-cotton yield in all s oil types evaluated. Cotton-yield suppression was greatest in response to R. reniformis at high Pi. Cotton maturity, measured as percentage of open bolls at different dates, was affected by the presence of nema todes in all 3 years.