Influence of environmental parameters on penoxsulam control of alligatorweed (alternanthera philoxeroides) in rice (oryza sativa)

摘要

Alligatorweed is a perennial plant which reproduces vegetatively and has spread fromwaterways into canals and ultimately into rice fields of Louisiana and Texas.Penoxsulam is a new acetolactate synthase (ALS) inhibiting broad-spectrum herbicidethat was registered for rice in 2005. Previous research on alligatorweed control hasfocused mainly in aquatic areas and in the rice producing regions of Louisiana with littlesuccess. Research is limited using penoxsulam for alligatorweed control in riceproduction and results vary between year and location. Variability could be due togrowth habit and resource allocation of this perennial species. Therefore, field andlaboratory experiments were conducted from 2004 to 2007 to: 1) evaluate the effects ofselect rice herbicides on alligatorweed control, 2) determine the absorption andtranslocation efficiency and the effect of propanil on penoxsulam in alligatorweed 3)access the environmental effects of temperature on penoxsulam efficacy and determineapplication timing to avoid antagonism with propanil and, 4) evaluate the effects offlood timing and rice cultivars on rice root stunting and plant foliar injury frompenoxsulam applications. Alligatorweed control was obtained from penoxsulam or bispyribac-sodium appliedalone; however, mixtures with propanil were antagonistic. Day temperatures at 21 Cincreased efficacy of penoxsulam compared to 27 and 30 C day temperatures. Delayingpropanil applications 3 days following penoxsulam applications were required at 21 and27 C and 10 days at 30 C in order to avoid antagonism. Alligatorweed absorbed up to33% of penoxsulam when applied alone, but most was retained in treated leaves (29%).Propanil reduced penoxsulam absorption into alligatorweed with only 22% of totalpenoxsulam recovered being absorbed by alligatorweed. More than 50% remained onthe leaf surface of the treated leaf. Previous research has indicated root stunting of riceplants from ALS inhibiting herbicides. When various rice varieties were permanentlyflooded one week after herbicide application of penoxsulam, root stunting was greatercompared to delaying flood establishment 7 or 14 days after treatment. Significant rootstunting, however, did not affect rice yield.