Relationship of Yields and Pratylenchus spp. Population Densities in Dryland and Irrigated Corn

Analyses of covariance were used to relate corn yields to population densities of Pratylenchus hexincisus in South Dakota dryland corn or P. scribneri in irrigated corn. The relationship for P. hexincisus was Y = 5,825 - 0.14X - 0.03X' where Y = yield (kg/ha), X = number of P. hexincisus per gram of dry root at midseason and X' = number at harvest. The relationship for P. scribneri was best described by Y = 7,400 - 0.06X' for nematode populations measured at harvest. Yield loss estimates indicated P. hexincisus was more damaging to dryland corn than was P. scribneri to irrigated corn.