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United States Department of Agriculture

Agricultural Research Service

Title: Effect of Mowing Prior to Applications of Picloram and Clopyralid on Russian Knapweed Control

Authors
item Carpinelli, Michael
item Ransom, Corey - OREGON STATE UNIV

Submitted to: Society for Range Management Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: December 1, 2003
Publication Date: January 24, 2004
Citation: Carpinelli, M.F., Ransom, C.V. 2004. Effect of mowing prior to applications of picloram and clopyralid on russian knapweed control. In: Proceedings of the Society for Range Management, 57th Annual Meeting. 2004 CDROM.

Interpretive Summary: Russian knapweed is a perennial weed that forms dense colonies by adventitious shoots arising from an extensive root system. It infests some of the most productive pasture and hayland of the Great Basin. Fall application of a soil-active herbicide may be an effective way to control Russian knapweed growth the following year. Recently developed equipment mows and applies herbicide in a single pass, removing standing dead plants and allowing more herbicide to reach the soil where it is taken up by plant roots. In a recently completed study, we tested two soil-active herbicides with and without mowing. Generally, Russian knapweed control using either herbicide was improved where preceded by mowing. This method may increase profits to hay and forage growers by reducing herbicide costs while improving control of Russian knapweed.

Technical Abstract: Russian knapweed is a perennial weed that forms dense colonies by adventitious shoots arising from an extensive root system. It infests some of the most productive pasture and hayland of the Great Basin. Fall application of a persistent, soil-active herbicide has been shown to effectively control Russian knapweed. The Brown Brush MonitorTM mows and applies herbicide in a single pass, removing standing dead plants and allowing more herbicide to reach the soil surface. We tested the hypothesis that mowing immediately prior to applying a soil-active herbicide in the fall increases Russian knapweed control and reduces Russian knapweed density and height in subsequent years. Using the Brown Brush MonitorTM, we tested two persistent, soil-active herbicides (picloram and clopyralid) with and without mowing at two sites in SE Oregon. Treatments were applied in fall 2001, and Russian knapweed control, density, and height were measured in summers 2002 and 2003. Results were inconsistent at Site 1. At Site 2, mowing increased Russian knapweed control by clopyralid in 2002 and by picloram in 2003, and reduced Russian knapweed height and density for both herbicides in 2003. Results from this study suggest that control of Russian knapweed may be improved by mowing prior to fall herbicide application, but that results may be site-specific.

Last Modified: 4/17/2014
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