Managing Mugwort In Field Nurseries With Cultivation And Herbicides

Date: 

2012 to 2013

Summary: 

A field study was established in 2012 to evaluate the effect that vigorous cultivation (rototilling) may have on improving the efficacy of currently registered herbicides. The target weed, mugwort (Artemisia vulgaris), has deep rhizomes that often allow it to escape complete control with available herbicides. If a late summer rototilling can reduce the size of the rhizomes and bring them closer to the surface, then fall-applied herbicides should be more effective in preventing the smaller rhizomes from regenerating shoots the following spring. The study was planned for two geographically separate nurseries with a similar weed problem. The site at Schichtel's Nursery in Springville, NY was successfully established in early October 2012. The results of those treatments are reported below.

Issue: 

Mugwort (Artemisia vulgaris L.) is a deciduous herbaceous perennial weed with deep rhizomes. This species has long been a weed problem for nurseries in parts of the Northeast. However, in the last two decades, mugwort has graduated from a marginal troublesome species to a major invasive weed that is rapidly expanding and colonizing fields and natural areas. One of the major reasons for its expansion is the lack of effective control available for field nursery production. As part of our IPM effort to manage this weed, we urge growers and managers to check for mugwort on incoming plant material and scout for small plants in the field. However, because mugwort can also disperse by seed, it is not possible to rely solely on scouting as a means of preventing movement into new areas. In general, cultivation and rototilling during nursery field production is not advised as a mugwort management technique because the cultivating implements break up rhizomes and spread the weed down the rows. Only a few options are available to manage this weed with herbicides. In upstate New York, there are three herbicides that have effective activity against this weed: Casoron (dichlobenil), Roundup (glyphosate) and Lontrel (clopyralid). On Long Island, the most effective of herbicide, clopyralid, is not available. The question arises whether manipulation of the timing of field cultivation might have a beneficial effect on the performance of the available herbicide tools.

Response: 

Our response was to conduct field research to explore management techniques to improve mugwort control.

Objectives:
1. Determine if late summer rototilling will improve the ability of currently registered herbicides to control mugwort when they are applied in late fall.
2. Evaluate the effect that late summer rototilling (alone) has on the regenerative ability of this rhizomatous weed.
3. A project evaluation was conducted in the spring 2013 to determine if there is a change in mugwort population due to these treatments.

Impact: 

The results of a preliminary stem count suggest that the most mugwort was emerging from plots that were rototilled in September but not October. The subplot with significant emergence was treated with glyphosate in October. The other treated plots had little or no mugwort emergence at the time of this preliminary evaluation.

The results from the data gathered in Spring 2013 indicate that the glyphosate treatment was more effective on non-tilled plots. It appeared that the tillage operation may have been too late in the season to allow sufficient numbers of rhizomes time to resprout before the glyphosate was applied.
The dichlobenil 4G was very effective regardless of tillage, indicating that the dichlobenil rate can be reduced and excellent control still be obtained. The spray formulation provided some mugwort control. The tilled plots were more susceptible to the spray formulation than the untilled, which indicates that tillage prior to application of a marginally effective treatment will help to increase the level of control. Clopyralid was adequate regardless of the tillage regime.

Casoron (Dichlobenil) is an expensive and usually only partially effective tool for managing this weed. If we can improve its effectiveness, then growers will realize an overall reduction in the population of mugwort. Additionally, they should be able to reduce supplemental spot treatments of glyphosate.
Outreach about the potential for more effective control of this weed has already included scheduled presentations to commercial growers and nursery managers. Also the information will be disseminated through CCE newsletters and grower IPM e-newletters.

Submitted by: 

  • Eshenaur, Brian C

Researchers involved: 

  • Eshenaur, Brian C
  • Senesac, Andrew

Organizations involved: 

  • Cornell Coopertive Extension of Suffolk County

International focus: 

  • United States of America
  • Canada

United States focus: 

  • New York