Date of Award

5-1-2010

Degree Name

Master of Science

Department

Plant and Soil Science

First Advisor

Walters, S.

Second Advisor

Young, Bryan

Abstract

Management of volunteer horseradish is a major challenge in fields when horseradish is included in the crop rotation. Three field studies were conducted: 1) to evaluate the growth habit and density of volunteer horseradish, 2) to evaluate the efficacy of fall herbicide applications for control of volunteer horseradish, 3) to evaluate the tolerance of subsequent horseradish crops to persisting soil residues of halosulfuron. One year following horseradish production, field infestations of volunteer horseradish ranged from 0.08 to 6.60 plants/m2 with the majority of plants emerging from established roots left below the depth of horseradish harvest and tillage. Fall herbicide applications provided effective control of volunteer horseradish compared to the nontreated control. Combinations of 2,4–D tank–mixed with glyphosate, iodosulfuron, halosulfuron, or rimsulfuron:thifensulfuron achieved the greatest control of volunteer horseradish and reduced volunteer horseradish densities to less than 1 plant /m2, while glyphosate alone provided the least control and density reduction. In addition to volunteer horseradish control, combinations of 2,4–D with glyphosate, iodosulfuron, halosulfuron, or rimsulfuron:thifensulfuron also provided 97% or greater control of winter annual weeds (henbit, common chickweed, and Carolina foxtail). Although the herbicide halosulfuron is very effective at controlling volunteer horseradish, it has the potential to injure future horseradish crops due to soil persistence. Field studies showed that after 4 months following a June halosulfuron application, horseradish can be replanted with no visual injury or reduction in root biomass. Tillage may provide temporary removal of volunteer horseradish plants, however, herbicide applications (e.g., 2,4–D with halosulfuron, iodosulfuron or rimsulfuron:thifensulfuron) provide the most consistent, complete control of volunteer horseradish.

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