|Norsworthy, J - CLEMSON UNIV|
|Carey, F - VALENT USA CORP|
|Talbert, R - UNIV OF ARKANSAS|
Submitted to: Weed Science
Publication Type: Review Article
Publication Acceptance Date: January 7, 2004
Publication Date: May 17, 2004
Citation: Hoagland, R.E., Norsworthy, J.K., Carey, F., Talbert, R.E. 2004. Metabolically - based resistance to the herbicide propanil in echinochloa species. Weed Science. 52:475-486. Technical Abstract: Propanil is an acylanilide herbicide introduced in the early 1960's to control dicotyledonous weeds and grasses including, Echinochloa species in cultivated rice (Oryza sativa L.). Since then, propanil has been used extensively in rice production in the United States and in several other countries. Propanil is an inhibitor of photosystem II, but rice is tolerant to propanil due to the presence of a high level of aryl acylamidase that catalytically degrades the compound to non-phytotoxic products, i.e., 3,4-dichloroaniline and propionic acid. As recently as ten years ago, biotypes of barnyardgrass [Echinochloa crus-galli (L.) Beauv.] and junglerice [E. colona (L.) Link] were discovered to be resistant to propanil applied at label recommended use rates. The mechanism of resistance of two biotypes of these two species has been shown to be elevated levels of aryl acylamidase activity. Various stages to combat propanil-resistance and to more fully understand the biochemistry involved in this resistance have been investigated. These include the interactions of other chemicals (herbicides and other chemicals) with propanil, rotation of rice with other crops (and consequently the use of other herbicide modes of action), and the use of alternative herbicides in rice. Certain compounds, including some organophosphate insecticides, are potent inhibitors of aryl acylamidase, and in some instances such compounds can act as synergists with propanil to increase phytotoxicity. Another compound (PPG-124), that lacks insecticidal or herbicidal activity, has been commercialized as a herbicide synergist for propanil. These chemical and biochemical interactions, and other factors involved in propanil-resistant Echinochloa weeds are presented and discussed.