Skip to main content
ARS Home » Southeast Area » Tifton, Georgia » Crop Protection and Management Research » People » Theodore Webster

Theodore Webster
headline bar

Theodore Webster, Research Agronomist



- Crop Science (Weed Science), North Carolina
   State University, Raleigh

- Agronomy (Weed Science), Ohio State
   University, Columbus

- Agronomy (Crop Science), Ohio State
   University, Columbus

Curriculum Vitae


My goal is to improve the efficiency of weed management systems through increased understanding of weed-crop interactions. Current research is directed towards the study of the ecology and management of three weeds: 1) nutsedges in vegetable cropping systems in the absence of methyl bromide, 2) Bengal dayflower (aka tropical spiderwort) in agronomic crops, and 3) glyphosate-resistant Palmer amaranth in agronomic crops.

Additional Information:

Georgia Weed Science Working Group web page:
Tropical Spiderwort Symposium, Tifton:
Ohio State University Perennial Weed ID Guide:


Side by Side ComparisonNontreated Control
Nutsedges are among the most troublesome weeds in vegetable crops in the Southeast US.
These weeds will readily punture through polyethylene mulch, compete with these crops for
resources, and reduce crop yields.  The challenge is to identify effective alternatives to
methyl bromide, an ozone-depleting substance, for management of nutsedges and other
weed, insect, plant pathogen, and nematodes pests.

Yellow nutsedge diagramPurple nutsedge diagram
In spite of visual similarities of purple nutsedge and yellow nutsedge, these two species have unique growth habits and require different management strategies. The drawings above illustrate the unique means by which tubers are distributed. Purple nutsedge will form long chains of tubers that will extend out from the initial tuber. In contrast, yellow nutsedge has a more compact growth habit with tubers in close proximity to the initial tuber and will not form long chains like purple nutsedge.
Purple nutsedge - no mulchPurple nutsedge - black mulch
The use of black polyethylene mulch, the standard practice for general weed suppression in Southeast vegetable production, promotes the growth of purple nutsedge. The figure with the yellow grids shows the 60 weeks of growth of a single purple nutsedge shoot without mulch (18 ft x 8 ft patch) and with black polyethylene mulch (24 ft x 18 ft patch). In contrast, yellow nutsedge growth is suppressed by black polyethylene mulch (see 2005 manuscripts for a full description).


Bengal dayflower (Commelina benghalensis) is an exotic invasive weed that has recently become a concern in agronomic crops of the Southeast US. Bengal dayflower, also known as tropical spiderwort, has become problematic due to significant changes in farming practices; specifically reduced tillage/elimination of in-crop cultivation, reduced usage of herbicides with soil residual activity, and increased cotton acreage planted (due to both boll weevil eradication and introduction of Roundup-tolerant varieties). Bengal dayflower is tolerant to glyphosate (Roundup) and many of the other commonly applied herbicides and can cause up to 60% yield loss in cotton and up to 100% yield loss in peanut. The presence of an underground flower (appears as a white swollen "tuber-like" structure, pictured below) makes this a very unusual weed and one that is difficult to eradicate due to the rapid rate of reproduction.
TSW seedling in corn field Tropical spiderwort infesting peanuts
Cotton from spiderwort heightTSW subterranean flower


Our crew over the years