Date of this Version
Weed Science, 1995. Volume 43:269-275
A simulation model was developed to predict the population dynamics and economics of velvetleaf control in a corn-soy bean rotation. Data compiled from the literature were used to parameterize the model f or two situations, one in which velvetleaf was infected by a Verticillium spp. wilt and one without infection. Verticillium was assumed to have no effect on corn or soybean yield. In the absence of control, simulated seed bank densities of a Verticillium-infected velvetleaf population were 5 to 50 times lower than for an uninfected velvetleaf population. The model was used to evaluate a threshold weed management strategy under the assumption that velvetleaf was the only weed and bentazon the only herbicide available for its control. In the absence of Verticillium, an economic optimum threshold of 2.5 seedlings 100 m-2 afforded the highest economic returns after 20 yr. of simulation. Simulations in which velvetleaf was infected in 8 out of 20 randomly assigned years indicated a 6% increase in annualized net return and an 11%reduction in the number of years that control was necessary. Sensitivity analysis indicated the parameter estimates having the greatest impact on economic optimum threshold were seedling emergence and survival, maximum seed production, and herbicide efficacy. Under an economic optimum threshold of 2.5 seedlings 100 m-2, management practices that manipulate the most sensitive demographic processes increased annualized net return by up to 13 % and reduced long-term herbicide use by up to 26%. Results demonstrate that combining an economic optimum threshold with alternative weed management strategies may increase economic return and reduce herbicide use. Nomenclature: Bentazon [3-(1-methylethyl)-(1H)-2,1,3-ben-zothiadiazin-4(3H)-one2 ,2-dioxide]; velvetleaf, Abutilon theophrasti Medicus #3 ABUTH; soybean, Glycine max (L.) Merr. 'Evans'; corn, Zea mays L.