2007 Annual Report
Identification of glyphosate tolerant Italian ryegrass populations from Mississippi. -- The intense use of glyphosate and continued adoption of glyphosate-resistant crops without rotation with non-glyphosate-resistant crops has increased the selection pressure to evolve resistance in certain weed populations. Scientists from Delta Research and Extension Center, Mississippi State University and USDA-ARS, Southern Weed Science Research Unit, Stoneville, MS, have characterized two Italian ryegrass populations from Mississippi, suspected to be tolerant to glyphosate. These two populations were 3-fold more tolerant to glyphosate compared to the susceptible population. This is the first report of glyphosate-resistant Italian ryegrass populations from glyphosate-resistant cotton and glyphosate-resistant soybean cropping systems.
Cogongrass. -- Cogongrass continues to spread northward in the U.S. Recent field surveys have determined its presence in more than 75% of the counties in Mississippi, including the first sites in agricultural and non-agricultural areas in the Yazoo-Mississippi Delta Region. A highly effective non-herbicide method of killing cogongrass using heat was developed by scientists at the Southern Weed Science Research Unit (SWSRU). Industry and public utilities and departments of transportation have yet to implement this new methodology.
Deeprooted sedge. -- Deeprooted sedge is an invasive weed that is spreading at an alarming rate in the southeastern US. Scientists at the Southern Weed Science Unit conducted cooperative studies to determine its spread and invasion in agricultural and natural areas. These published studies indicated that deeprooted sedge has the capability to continue to spread and infest areas in addition to the currently known sites in 64 counties in six southeastern states.
Rye cover crop-based cotton production. -- The use of a rye cover crop in cotton promoted the growth and establishment of brown top millet, a serious weed in cotton. It is not clear whether the rye acted as a barrier to herbicide treatment resulting in less herbicide damage to the millet or provided an environment more favorable to its growth. Browntop millet can pose a serious threat to cotton because its long stems and leaves intertwine with cotton fiber during harvest resulting in excessive cotton fiber contamination during ginning. These results show that each component of a crop management scenario must be evaluated completely in order to establish its contribution, whether negative or positive, to crop production. In this case, cover crops can provide negative results on weed populations and have detrimental consequences in crops such as cotton.
Bryson, C.T., Koger III, C.H., Byrd, J.D. 2007. Effects of temperature and exposure period to heat on cogongrass (imperata cylindrical) viability. Weed Technology 21:141-144.
Reddy, K.N., Locke, M.A., Koger III, C.H., Zablotowicz, R.M., Krutz, L.J. 2006. Cotton and corn rotation under reduced tillage management: impacts on soil properties, weed control, yield, and net return. Weed Science 54:768-774.
Nandula, V.J., Poston, D.H., Reddy, K.N., Koger Iii, C.H. 2007. Formulation and adjuvant effects on uptake and translocation of 14**c clethodim in bermudagrass (cynodon dactylon). Weed Science 55:6-11.
Nandula, K.K., Poston, D.H., Eubank, T.W., Koger III, C.H., Reddy, K.N. 2007. Differential Response to Glyphosate in Italian Ryegrass (Lolium multiflorum) Populations from Mississippi. Weed Technology 21:477-482.
Bettmann, G.T., Ratnayaka, H.H., Molin, W.T., Sterling, T.M. 2006. Physiological and antioxidant responses of cotton and spurred anoda (anoda cristata)under nitrogen deficiency. Weed Science 54:641-650.
Molin, W.T., Boykin, D.L., Hugie, J.A., Ratnayaka, H.H., Sterling, T.M. 2006. Spurred Anoda (Anoda cristata) Interference in Wide Row and Ultra Narrow Row Cotton. Weed Science. 54:651-657.
Rosen, D.J., R. Carter, and C.T. Bryson. 2006. The recent spread of Cyperus entrerianus (Cyperaceae) in the southeastern United States and its invasive potential in bottonland hardwood forests. Southeastern Naturalist 5:333-344.
Sanyal, D., Bhowmik, P.C., Reddy, K.N. 2006. Influence of leaf surface micromorphology, wax content, and surfactant on primisulfuron droplet spread on barnyardgrass and green foxtail. Weed Science 54:627-633.
Nandula, V.K., Eubank, T.W., Poston, D.H., Koger Iii, C.H., Reddy, K.N. 2006. Factors effecting germination of horseweed (conyza canadensis). Weed Science. 54: 898-902.
Burke, I.C., Koger Iii, C.H., Reddy, K.N., Wilcut, J.W. 2007. Reduced translocation is the cause of antagonism of glyphosate by msma in browntop millet (brachiaria ramose) and palmer amaranth (amaranthus palmer). Weed Technology 21:166-170.
Nandula, V.K., Reddy, K.N., Rimando, A.M., Duke, S.O., Poston, D.H. 2007. Glyphosate resistant and susceptible soybean (Glycine max) and canola (Brassica napus) dose response and metabolism relationships with glyphosate. Journal of Agricultural and Food Chemistry 55:3540-3545.
Zablotowicz, R.M., Reddy, K.N. 2007. Nitrogenase activity, nitrogen content, and yield responses to glyphosate in glyphosate-resistant soybean. Crop Protection Journal 26:370-376.
Koger Iii, C.H., Burke, I.C., Miller, D.K., Kendig, A.J., Reddy, K.N., Wikut, J.W. 2007. Msma antagonizes glyphosate and glufosinate efficacy on broadleaf and grass weeds. Weed Technology. 21:159-165.