| Abstract/Contents: | "Sericea lespedeza (Lespedeza cuneata), and introduced, allelopathic, long-lived perennial legume is becoming a major weed problem in pastures of southeastern U. S. and currently is listed as a noxious weed in some Kansas counties. It becomes unpalatable to cattle with increasing maturity due to increasing tannin content. When not grazed, sericea lespedeza is very competitive with other forage species, and quickly becomes the dominant species. In addition, sericea lespedeza is tolerant of commonly used pasture herbicides (2,4-D, picloram and dicamba) and control with triclopyr and metsulfuron-methyl is often short-lived. Re-establishment of serieca lespedeza, from original plants not controlled and from seedlings, was evaluated in three herbicide experiments initiated in 1995. Two experiments were in bermudagrass pastures and the third on a tallgrass prairie site. Treatments were arranged in randomized complete block design with four replications, and included: no herbicide, triclopyr at 8.0 oz ae/A and metsulfuron-methyl ant 0.18 oz ai/A applied at three stages of plant developmment; early vegetative (June), late vegetative (July), and bloom (September). Stem densities from original plants were taken 1 and 2 YAT [Year(s) Afterr Treatment]. Significant (P<0.05) site by treatment interaction between bermudagrass and tallgrass prairie sites precluded pooling across all locations. Interaction was attributed to differences in stems remaining 1 and 2 YAT with metsulfuron-methyl. Treatment mean comparisons were separated using a general linear model least significant difference test at the 5% significance level. For the pooled bermudagrass sites, percent stems of sericea lespedeza remaining 1 YAT with triclopyr were 3,2, and 13 % respectively for June, July, and September applications, with no significant difference due to time of application. By 2 YAT, percent stems remaining with triclopyr were 10, 13, and 29% for June, July, and September applications, with no significant difference among applications. Stems of sericea lespedza remaining 1 YAT with metsulfuron-methyl in bermudagrass pastures were 51, 16, and 6 % for June, July and September applications, with stems densities for June application being significantly greater than densities with July and September applications. Percent stems remaining 2 YAT with triclopyr applied in June, July, and September were 1,0 and 8% respectively, with no significant difference due to time of application. Percent stems remaining 2 YAT with metsulfuron-methyl were 87,25, and 26% with stem densities for June application being significantly greater than July and September applications. For the tallgrass praire site, sericea stems remaining 1 YAT with triclopyr applied in June, July, and September were 1, 0, and 8% respectively, with no significant difference due to time of application. Percent stems remaining 2 YAT with triclopyr were 17, 6, and 55%, with densities for September applications being significantly greater than densities with June and July applications. Application of metsulfuron-methyl at the tallgrass prairie site resulted in 41, 6, and 0% stems remaining 1 YAT, with stem density for June application being significantly greater than stem densities from July and September applications. By 2 YAT, percent stems remaining with metsulfuron-methyl were significanlty greater for June and July applications with 95 and 69% stems remaining, compared to 36% for September application. Seedling densities of sericea lespedeza at the bermudagrass sites varied from 4 to 8/sq ft for treatments where extablished sericea lespedeza was controlled in 1995, compared to 23/sq ft in the untreated plots. At the tallgrass prairie site, there were 12 seedlings/sq ft in untreated plots, compared to 6/sq ft with June application of metsulfuron-methyl and 2 to 4/sq ft for other herbicide treatments. Differences in seedling densities between the bermudagrass and tallgrass prairie sites may be attributed to different grazing systems used at the sites. At the bermudagrass site, intensive continuous grazing kept the bermudagrass short, resulting in little competition for emerging seedlings. At the tallgrass prairie site, light grazing resulted in upright growth of species competing with emerging seedlings. A fourth experiment was initiated in 1997 to evaluate the response of seedling sericea lespedeza to five POST herbicides. The site used was an area where seedling sericea lespedeza emerged in 1997 from an area where established plants of sericea lespedeza were controlled with mowing plus herbicides in 1995. Treatments evaluated were arranged in randomized complete bock [block] design with four replications. Treatments were applied June 5, 1997 and included: no herbicide, metsulfuron-methyl at 0.06 and 0.12 oz ai/A, triclopyr at 4.0 oz ae/A, picloram plus 2,4-D at 1.0 and 4.0 oz ae/A, and dicamba plus 2,4-D at 6.0 and 2.0 oz ae/A. Seedling densities were taken June 5 and November 14, 1997. Seedling densities were significantly reduced 71% with mesulfuron-methyl at 0.12 oz ai/A when compared to no herbicide (25%). Seedling reductions with the other herbicide treatments were not signifcantly different from the untreated control." |
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