Name: Dr. Theodore M. Webster

Title: Research Agronomist

Research: Integrating weed control technology and knowledge of weed biology to improve the efficiency of weed management systems.

Support Staff: Eddie Sklany and James Davis

Address:
Crop Protection and Management Research Unit
USDA-ARS, University of Georgia, Tifton Campus
PO Box 748
Tifton, GA 31793-0748

Phone: 229-386-3363

Fax: 229-386-3437

Email: Twebster@tifton.usda.gov

Education:
B.S. Agriculture, Ohio State University (1991)
M.S. Agronomy, Ohio State University (1993)
PhD. Crop Science, North Carolina State University (1996)

CRIS Project Title: Integrated Management and Ecology of Weed Populations
in the Southeastern Coastal Plain

CRIS Research Goals:

1) Develop integrated weed management systems for selected agronomic and vegetable crops with emphasis on reducing herbicide use by improving crop production efficiency through a balanced weed management system, reducing cropping system vulnerability to weed establishment, and minimizing weed propagule production.

2) Conduct basic research on weed-crop ecology in irrigated and reduced tillage systems by correlating environmental factors with weed emergence, evaluating shifts in weed species composition in cropping systems with various rotations and tillage intensities, and determining the effect of post-harvest weed management practices on the soil seedbank.

3) Evaluate alternative methods for managing weeds in vegetable crops without methyl bromide fumigation: determine the potential of solarization for weed management, assess the efficacy of currently registered technologies in vegetable crops as alternatives to methyl bromide, evaluate new technologies in vegetable crops to replace methyl bromide, and integrate alternatives to methyl bromide fumigation into vegetable crop production systems.

Current Research Projects:

1) Alternatives to methyl bromide for management of nutsedges in vegetables using new technologies (e.g. halosulfuron).

2) Alternatives to methyl bromide using current technologies (e.g. fumigants).

3) Ecology of nutsedges in crop production systems.

4) Perennial weed management (bermudagrass and nutsedges)

5) Ecology and management of Commelina benghalensis (tropical spiderwort); an exotic, Federally noxious, invasive weed.

6) Cultural practices affect weed-crop interactions and weed species composition

Major Accomplishments over the life of the project:

The effectiveness of polyethylene mulches in suppressing nutsedge growth was evaluated in the wake of the impending elimination of methyl bromide. In greenhouse studies, purple and yellow nutsedge growth was monitored in pots covered with black polyethylene mulch, clear polyethylene mulch, or not covered. Relative to the non-mulched treatments, mulches reduced yellow nutsedge tuber production 50% and shoot populations 96%, while there were no differences among the treatments for purple nutsedge. Polyethylene mulch can be an important component of a yellow nutsedge management system, while other factors will need to be explored for successful management of purple nutsedge.

Research was conducted to adapt and validate a computer-based weed management decision support system (HADSS) that utilizes weed biology, efficacy of weed control, and economics to make weed control recommendations in Georgia. The incumbent worked with the model developers at North Carolina State University, extension personnel at the University of Georgia, and county agents in Georgia to conduct field validation of the model. Significant alteration in the database have made HADSS a suitable tool for Georgia growers, closely approximating the recommendations of Georgia extension specialists. The validated HADSS model has been released for Georgia, assisting county extension agents, consultants, growers, and university scientists in making weed management recommendations, as well serving as a training tool to instruct each of these groups concerning the complex interactions among weed biology, weed control, herbicide efficacy, and economics.

The search for methyl bromide alternatives in vegetable crop systems has led to the exploration of alternative technologies, including solarization which has long been rumored to be an effective means of reducing weed populations. Studies were initiated to evaluate the combined effect of heat treatments and durations of exposure on the viability of tubers of purple nutsedge and yellow nutsedge, the primary means of reproduction for these weeds. Purple nutsedge tubers were shown to be more tolerant of elevated temperatures than were yellow nutsedge tubers, however elimination of tubers viability was achieved. Using the available technology solarization can not be relied upon as a means of reducing nutsedge tuber viability due to the inability to raise soil temperatures for critical durations of exposure.

Links:

University of Georgia/ARS Weed Science Webpage (contains some of my slide presentations): http://www.GAWeed.com

Georgia Cotton HADSS (a web-based interface of the Georgia version of the Herbicide Application Decision Support System, tailored to Georgia by T.M. Webster and A.S. Culpepper): http://www.webhadss.ncsu.edu/LocationIntro.asp?Location=Georgia

Perennial Weed Identification Guide (Developed while I was at the Ohio Agricultural Research and Development Center in Wooster, Ohio): http://www.oardc.ohio-state.edu/weedguide/

Community of Science: http://myprofile.cos.com/webster39