Canada Thistle/Horse Nettle/Dewberry

Canada Thistle/Horsenettle/Dewberry

Abstracts:

• Effectiveness of Some Newer Herbicides on Selected Broadleaf Perennial Weeds in Corn. T. J. Fritz, W.S. Curran, and N. L. Hartwig, 1992. Proc. NEWSS 46:30-31.

Effectiveness of Some Newer Herbicides on Selected Broadleaf Perennial Weeds in Corn. T. J. Fritz, W.S. Curran, and N. L. Hartwig, 1992. Proc. NEWSS 46:30-31.

Perennial weeds in corn seem to be increasing in Pennsylvania. Nicosulfuron, primisulfuron, clopyralid, and dicamba were evaluated on horsenettle (Solanum carolinense L.), and Canada thistle (Cirsium arvense L.) during the 1991 growing season. In addition, the efficacy of these materials excluding clopyralid were also evaluated in 1990 and 1991 on dewberry (Rubus sp.).

Extension agents in Erie, Montgomery and York counties located fields with moderate horsenettle infestations and conducted identical trials. Each location was a randomized complete block design with 4 replications. Identical treatments were applied postemergence at a early and late timing. Rates applied (lb/A) were as follows: nicosulfuron, 0.031 and 0.062; primisulfuron, 0.036 and 0.071; clopyralid, 0.125 and 0.25; and dicamba, 0.25 and 0.5, respectively. The York County results were poor due to drought and insect damage. Erie and Montgomery County results were more similar to one another. Primisulfuron and dicamba provided the best control, while nicosulfuron and clopyralid did not show much activity. Optimum application timing could not be determined by these trials. Late applications performed better at Erie, while the early applications performed better at Montgomery. Higher rates generally performed better than lower rates, although not consistently.

A postemergence randomized complete block design with 3 replications was used to evaluate control of Canada thistle. Clopyralid (0.094 and 0.25 lb/A) was applied at an early and late timing at both rates. Dicamba was applied at the high rate (0.5 lb/A) during the early application and at the low rate (0.25 lb/A) during the late application timing. Nicosulfuron (0.031 lb/A) and primisulfuron (0.036 lb/A) were applied during the late timing. Trends were as follows: clopyralid applied during the late application performed the best, dicamba applied at the high rate early performed better than the low rate applied later, primisulfuron was fair, and nicosulfuron was poor.

A randomized complete block design with 3 replications was used to evaluate control of dewberry in 1990 and 1991. Postemergence treatments of nicosulfuron (0.031 and 0.047 lb/A), atrazine (2.0 lb/A), dicamba (0.25 lb/A), and primisulfuron (0.036 and 0.054 lb/A) were applied. None of the herbicides were very effective the year of application. In the second year evaluation of the 1990 application year, nicosulfuron provided excellent control, while atrazine control was fair. Control of dewberry was poor for dicamba and primisulfuron.