Chemical Control of Wolfweed in South Texas

Abstract

Wolfweed, which is considered undesirable due to its lack of wildlife or agricultural value, forms dense colonies that inhibit the growth of other plants. We hypothesize that herbicide application following a mechanical treatment, such as shredding, will result in better control of this plant. The objective was to evaluate the effectiveness of a combination of the herbicides Picloram and 2, 4-D and shredding on wolfweed control. The study site is located in south Texas, in McMullen County. Treatments were randomly allocated in three blocks on shredded and non-shredded stands of wolfweed. Herbicide used was the combination of Picloram (10.2%) and 2, 4-D (39.6%). Three treatments were evaluated: recommended dose (RD), 1% of the herbicide in water; half of the recommended dose (HD), 0.5% of the herbicide in water; and control (C). A randomized complete block design in a 2x3 factorial arrangement of treatment and three replicates was used to evaluate these treatments. Response variable was percentage of mortality of wolfweed. ANOVA was used for statistical analysis and the Duncan’s multiple range test was employed as a means separation procedure. No significant (P>0.05) interaction was found between factors. The percentage of mortality in wolfweed after application of the herbicide on the shredded area was similar for RD (19.9%) and HD (16.6%), but different (P<0.05) from C (0%). On the non-shredded area wolfweed mortality was similar for RD (52.1%) and HD (46.6%), but different (P<0.05) from C (1.8%). These results suggest that using half the recommended dose of this herbicide mixture provide similar control of wolfweed as the recommended dose. Additionally, a higher wolfweed mortality level was obtained when applying the herbicide to non-shredded stands.