An Alternative Approach for Evaluating the Efficacy of Potential Biocontrol Agents of Weeds. 1. Inverse Linear Model

Authors

Dan J. Pantone, University of California - Davis
William Williams, Louisiana Agricultural Experiment Station, Baton Rouge
Armand R. Maggenti, University of California - Davis

Date of this Version

11-1989

Comments

Published in Weed Science (November 1989) 37(6): 771-777.

Abstract

Methods for evaluating the efficacy of potential classical biocontrol agents were outlined for a model biocontrol agent-weed-crop system. A proposed biocontrol agent (the fiddleneck flower gall nematode), its weed host (coast fiddleneck), and wheat were used as representative organisms. An additive experimental design (inverse linear model) was used. Regression of the reciprocal of the average plant biomass of each species onto the density of itself and the other plant species yielded competitive indices that measure the competitive ability of the plants. The results of two years of field experiments revealed a dramatic change in the competitive interaction between fiddleneck and wheat due to the nematode. During the 1986-1987 season in the absence of the nematode, fiddleneck intraspecific competition was 33 times stronger than interspecific competition with wheat. In the presence of the nematode, intra- and interspecific competition of fiddleneck were nearly equal. Only the coefficients that measure interspecific competition changed significantly in the presence of the nematode while the coefficients for intraspecific competition did not.

Nomenclature: Coast fiddleneck, Amsinckia intermedia Fischer and Meyer #3 AMSIN; wheat, L. 'Anza'; fiddleneck flower gall nematode, Anguina amsinckiae (Steiner and Scott, 1935) Thorne, 1961.