First Report of Herbicide-Resistant <i>Echinochloa crus</i>-<i>galli</i> in Uruguayan Rice Fields

• Main Authors: Claudia Marchesi, Nestor E. Saldain
• Format: Article
• Language: English
• Published: MDPI AG 2019-11-01
• Series: Agronomy
• Subjects: barnyardgrass; propanil; quinclorac; penoxsulam; imazapyr + imazapic
• Online Access: https://www.mdpi.com/2073-4395/9/12/790

<i>Echinochloa crus-galli</i> is the main weed in direct dry-seeded rice systems worldwide and is the target of most herbicide applications. Numerous cases of <i>E. crus-galli</i> biotypes with resistance to herbicides have been reported in different regions of the world; however, to date, no cases have been reported in Uruguay. The purpose of this research is to assess the presence of herbicide-resistant <i>E. crus-galli</i> in the rice fields of Uruguay. More than 40 <i>E. crus-galli</i> biotypes were sampled from eastern to northern regions in different years and assessed following the Herbicide Resistance Action Committee (HRAC) protocols of confirmation, using the herbicides propanil, quinclorac, clomazone, bispyribac&#8722;sodium, penoxsulam, imazapyr + imazapic, profoxidim and cyhalofop. Herbicides rates included 0, 0.125, 0.25, 0.50, 1, 2, 4 and 8 times the label rate. Most <i>E. crus-galli</i> biotypes (35) resulted as resistant to quinclorac. Furthermore, resistance was confirmed to propanil in at least seven biotypes, 12 to imazapyr + imazapic, and three to penoxsulam. Five biotypes showed multiple resistance to propanil and quinclorac, and one biotype was resistant to quinclorac, penoxsulam and imazapyr + imazapic. No biotype showed confirmed resistance to clomazone, bispyribac-sodium, cyhalofop or profoxidim&#8212;herbicides that ensure satisfactory control. The presence of <i>E. crus-galli</i> herbicide resistant-biotypes reduces herbicide options, threatening rice production in Uruguay. In this context, a redesign of the productive systems would represent an opportunity to complement the chemical control, integrating larger-scale cultural and management practices.