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Department of Horticulture and Crop Science


HCS Colloquium

Oct 30, 2013 (All day)

Presenter:  Tyler Johnson
Advisor:  Dr. Mark Loux, Department of Horticulture and Crop Science

Proposal type: Masters proposal

Title of presentation: Influence of Cereal Rye and Annual Ryegrass Cover Crops on Management of Glyphosate-Resistant Horseweed

Abstract:  Horseweed (Conyza canadensis) populations with resistance to glyphosate have been a problem in the Midwestern United States for more than a decade.  Soybean growers continue to have problems obtaining consistently effective control of these populations, even with comprehensive herbicide programs.  There has been a general increase in the acres planted with winter cover crops in Ohio, and there is hope that the integration of cover crops in horseweed management programs can improve control.   Results of previous research have shown that cover crops can reduce horseweed germination in the spring, and compete with the weed for essential nutrients.  Of the viable cover crops for the Midwest, cereal rye (Secale cereale) and annual ryegrass (Lolium multiflorum) are well suited because of the species’ winter hardiness, biomass accumulation, and in the case of cereal rye, allelopathic activity.  Various groups of benzoxazinoids are released by rye, and these can inhibit the germination of horseweed.  The objectives of this study are to determine the effect of cereal rye and annual ryegrass on horseweed population density, the control provided by herbicides, and soybean grain yield.  Control of horseweed in the absence or presence of the cover will be studied over two crop seasons on multiple grower fields and at an OARDC station.  The treatment design will include the following additional factors:  (1) late fall application of 2,4-D vs none; (2) early vs late spring termination (burndown) of the cover with glyphosate; and (3) inclusion of herbicides in the burndown application that have residual activity on horseweed vs none.  Measurements in the study include population density of the cover at the time of termination, horseweed population density at various times from late fall through soybean harvest, horseweed control, and soybean yield.  The results of this research will provide information to OSU Extension educators, growers, and crop advisors about the value of cover crops in management of an important weed in Ohio, and how to optimize the other factors in herbicide programs to ensure consistent control.

11:30 AM Wednesday, October 30, 2013
244 Kottman Hall (Columbus)
video-linked to 
121 Fisher Auditorium (Wooster)