Master of Science (MS)


Plant Pathology and Crop Physiology

Document Type



Field studies were conducted over two years in drill- and water-seeded rice to evaluate weed control and crop response with imazethapyr programs. Barnyardgrass [Echinochloa crus-galli (L.) Beauv.] was evaluated with imazethapyr applied alone at various rates and timings. Imazethapyr controlled barnyardgrass 95 to 97% with a soil application at 87 or 70 g/ha fb 53 or 70 g/ha EPOST or LPOST. A single EPOST application of imazethapyr at 140 g/ha controlled barnyardgrass and rice yield was equal to or above those treatments receiving two applications of imazethapyr. Research was also conducted at Crowley, LA and Rayne, LA to evaluate the addition of a herbicide with broadleaf activity into imazethapyr programs applied alone early postemergence (EPOST) and in combination with imazethapyr postemergence (POST). Weeds evaluated included barnyardgrass, red rice (Oryza sativa L.), alligatorweed [Alternanthera philoxeroides (Mart.) Griseb.], and hemp sesbania [Sesbania exaltata (Raf.) Rydb. ex A.W. Hill]. Treatments consisting of imazethapyr applied at 87 g/ha alone to the soil fb a POST imazethapyr application at 53 g/ha controlled barnyardgrass above 90% late season in all studies, expect in water-seeded rice when an imazethapyr application was made at the three- to four-leaf rice stage. Red rice control with a total imazethapyr program was equivalent to, or higher, than other treatments in both drill- and water-seeded studies. Single imazethapyr applications resulted in reduced control of red rice indicating two applications of imazethapyr are required to obtain adequate control. Alligatorweed control increased with soil applications of imazethapyr. However, alligatorweed control with imazethapyr as the only herbicide in a weed control program was inconsistent and suggested only suppression. Treatments receiving a broadleaf herbicide application increased hemp sesbania control as compared with the total imazethapyr program; however, treatments with bensulfuron and triclopyr were inconsistent at controlling hemp sesbania. In drill-seeded studies, hemp sesbania was less of a problem and red rice had a greater impact on rice yield. Rice yields with total imazethapyr programs were equal to, or higher than, other treatments. However, in water-seeded studies, hemp sesbania growth was favored and yields from rice treated with broadleaf herbicides were higher than total imazethapyr programs.



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Committee Chair

Eric P. Webster