Weed Science


Hand-harvesting weeds from a treatment containment ring.


An experimental preemergence herbicide treatment is applied with a CO2 backpack sprayer.


Application of herbicide for management of weedy rice.


Transplanting aquatic weeds for future treatment with an experimental herbicide.

Dr. Webster’s research program has focused on weed control in conventional rice and herbicide-resistant rice. Research results have directly influenced the language and application methods for Command (clomazone) use in rice. Producers can apply Command at an economical price in both drill- and water-seeded rice. Command received a full federal label in 2000, and the label was further expanded because of the work conducted by Dr. Webster. This expansion included the use of Command in water-seeded rice by the impregnation of Command on fertilizer granules. This allowed for the application of Command by air onto saturated fields without the risk of off-target movement by aerial spray. Several other experimental herbicides have been evaluated over the years, and many of them received full federal labels, and each has a fit in Louisiana rice production. Regiment is an excellent herbicide for mid- to late-season barnyardgrass and broadleaf weed control for use in drill- and water-seeded rice. This product received a full federal label in 2001, and his project directly influenced how this product is used in Louisiana. Other herbicides that have received federal labels with support of research generated from his project include Aim (carfentrazone), Clincher (cyhalofop), RiceStar HT (fenoxaprop), Permit Plus (halosulfuron plus thifensulfuron), League (imazosulfuron), Grasp (penoxulam), Grasp Extra (penoxulam plus triclopyr), RebelEx (penoxulam plus cyhalofop), RiceBeaux (propanil plus thiobencarb), RiceOne (clomazone plus pendimethalin), Sharpen (saflufenacil), Provisia (quizalofop) and several others.

In 2002, rice varieties became available to producers that are tolerant to the herbicide imazethapyr and imazamox sold under the trade names Newpath and Beyond, respectively. This new technology has significantly changed weed control programs in Louisiana. For the first time, producers had the ability to control red rice with no detrimental effect on the rice crop. Dr. Webster’s project was on the leading edge in development of imidazolinone-resistant rice sold under the trade name Clearfield Rice. He conducted research on application timings, economics, impact of flood depths and flood timings on herbicide activity, weed removal timings, use of other herbicides in Clearfield rice production, and planting methods with this new technology. Research has directly influenced how Newpath is used in Clearfield rice in Louisiana and other states across the rice belt, and his research directly impacted the wording of the Newpath, Beyond and Clearpath, a pre-package mixture of imazethapyr plus quinclorac, labels. Dr. Webster continues to work with Clearfield rice. He is currently evaluating the use of propanil containing herbicides in mixture with Newpath and Beyond to increase control of red rice, and his project has documented synergism when the products are applied in mixture for red rice and barnyardgrass control.

Clearfield hybrid rice has been grown in Louisiana for several years. The parents used in the breeding of hybrid rice can have shattering and dormancy characteristics, and these traits can be passed on to the F1-hybrid. The shattering and dormancy of the hybrid is especially a problem if the rice is allowed to mature past optimum moisture prior to harvest or shattering occurs due to high winds, violent thunderstorms, tropical storms or hurricanes. A percentage of these plants also carry the imidazolinone resistance trait. Many fields have been in hybrid production for several years with no rotation, and these fields have developed a weedy rice problem. Some fields have been abandoned due to heavy weedy rice infestations. Dr. Webster’s project has been the lead for developing programs for the management of weedy rice infestations.

In the past few years, with the commercialization of Clearfield Rice, late season infestations of hemp sesbania [Sesbania herbaceae (Mill.) McVaugh] and Indian jointvetch (Aeschynomene indica L.) have become a problem. Dr. Webster’s project is currently determining the early and late season competitiveness of these weeds and the sphere of influence of these weeds on Clearfield rice. His work has also led to label expansion for Permit and Permit Plus as salvage treatments for late emerging weeds.

Dr. Webster’s program has also conducted research on the weed biology, plant ecology, and management of brook paspalum (Paspalum acuminatum Raddi), creeping rivergrass [Echinochloa polystachya (Kunth) Hitchc.], knotgrass (Paspalum distichum L.), Peruvian watergrass [Luziola peruviana (Juss.) ex. J.F. Gmel.], southern watergrass [Luziola fluitans (Michx.) Terrell & H. Rob] and water paspalum (Paspalum hydrophilum Henrad). These invasive perennial grasses are infesting rice fields in south Louisiana and Texas. Dr. Webster’s project has developed management strategies for these weeds by increasing the understanding of how they develop, grow and reproduce. In 2013, research began with the invasive annual grass Nealley’s sprangletop (Leptochloa nealleyi Vasey). This species has quickly established across the state of Louisiana and Texas rice production.

In 2008, Dr. Webster’s group developed a weed identification publication. To date, over 8,000 of these publications have been distributed. This publication has become the standard for rice weed identification. It is used as an educational tool in a Weed Science course at Texas A&M, and it is used by several companies and extension specialists to educate employees, consultants, and producers on weed identification. Thousands of copies have been printed online, and it is often requested internationally by those interested in rice weed identification. This publication can be found online at:


Herbicide drift has become a serious issue in rice production with the adoption of glyphosate- and glufosinate-resistant crops and Clearfield rice. Dr. Webster’s group published an extension publication to help those trying to diagnose herbicide drift in rice. This publication can be found online at:


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