Economic Analysis of Managing Multiple Pests in Tobacco. H. Walker Kirby, Department of Plant Pathology, North Carolina State University, Raleigh 27650. C. E. Main, Department of Plant Pathology, and G. A. Carlson, Department of Economics and Business, North Carolina State University, Raleigh 27650. Plant Dis. 67:1099-1102. Accepted for publication 14 April 1983. Copyright 1983 American Phytopathological Society. DOI: 10.1094/PD-67-1099.

Field experiments were conducted yearly from 1978 through 1980 to determine the effects of three selected nematicides plus an untreated control in combination with three economic threshold levels for tobacco budworms (Heliothis virescens) in tobacco fields known to have low populations of all nematodes, particularly root-knot species (Meloidogyne spp.). Effects on yield, value, and leaf quality were studied. Analysis of variance and regression analysis were used to characterize the effects of the combination treatments and pesticide expenditures related to gross returns. No significant differences were detected by analysis of variance, but regression analysis with an expanded model indicated that pesticide expenditures influenced gross returns. Quadratic regression models best fit the data and were used to characterize the relationship between gross returns and pesticide expenditures, postseason root-knot larval population densities, and selected weather variables.