Seasonal Dynamics and Yield Relationships of Pratylenchus spp. in Corn Roots.

The seasonal distribution of Pratylenchus spp. in seminal and adventitious roots and the relationship of maize yield variables to nematode densities were examined for irrigated maize in sandy soil in 1994 and 1995. Nematode populations in seminal roots were stable or declined (P </= 0.05) during the growing season, whereas total numbers of nematodes in adventitious root systems increased in both years of the study. Late-season nematode densities in adventitious roots were better related to midseason densities in seminal than adventitious roots. Seed test weights were negatively related to Pratylenchus spp. densities in seminal roots in both years (P </= 0.05) but inconsistently related to adventitious root populations. Maize yield was inversely related to early-season nematode densities in seminal roots in 1995 (P </= 0.03). Regression analyses indicated a 1% loss in seed test weight for each 10-fold increase in nematode density and a 1% loss in seed yield for each 1,000 nematodes/g root.