title: Com yield increases relative to nonfumigant chemical control of nematodes.
abstract: Corn yields were measured after application of nematicides in 16 experiments, mostly in medium-to-heavily textured soil, at 12 locations in Iowa during 1973-1976. The average maximum yield increase in plots treated with nematicides was 21% over yields in untreated plots. Yields were correlated negatively with nematode numbers or nematode biomass in nearly all comparisons. Correlations of nematode numbers in the soil with yield averaged -0.56 for Helicotylenchus pseudorobustus, -0.45 for Hoplolaimus galeatus, -0.51 for Pratylenchus spp., and -0.64 for Xiphinema americanum. Correlation coefficients for numbers of nematodes in the roots and yield averaged -0.63 for Pratylenchus spp. and -0.56 H. galeatus. Correlation coefficients for yield and total number of nematodes averaged -0.65 in roots and -0.55 in soils. Negative correlations also were greater for comparisons of yield with total parasitic-nematode biomass than with numbers of individual nematodes of a species or total numbers of parasitic nematodes.
authors.affiliation: Departments of Botany and Plant Pathology, Iowa State University, Ames, USA.
authors.forename: D C
authors.initials: DC
authors.lastname: Norton
authors.forename: J
authors.initials: J
authors.lastname: Tollefson
authors.forename: P
authors.initials: P
authors.lastname: Hinz
authors.forename: S H
authors.initials: SH
authors.lastname: Thomas