Wild Oat (Avena fatua) Populations Resistant to Triallate Are Also Resistant to Difenzoquat

Abstract

In response to farmer complaints of poor triallate performance, wild oat seed was collected from 34 fields in Alberta in the fall of 1990. Screening trials in the greenhouse indicated that 15 of the populations were highly resistant to triallate applied at the equivalent of the recommended field rate (1.7 kg ha-1), whereas the other 19 populations were adequately controlled. All triallate-resistant populations were also highly resistant to difenzoquat applied at 1.7 kg ha-1(equivalent to twice the recommended field rate). The effect of increasing rates of both herbicides on dry weight of five of the resistant and two of the susceptible populations was determined in greenhouse experiments. Triallate applied up to 3.4 kg ha-1had little or no effect on the resistant populations, whereas the susceptible populations were controlled at 1.7 kg ha-1. At rates of 6.8 kg ha-1or higher, there were differences among the resistant populations and among individuals within the populations in the response to triallate. Response of the resistant populations to increasing difenzoquat rates was variable between experiments, but in all cases the effect of difenzoquat on wild oat dry weight was considerably less in triallate-resistant than triallate-susceptible populations. Effects of increasing rates of triallate and difenzoquat on resistant and susceptible wild oat populations growing with barley in field experiments were generally similar to the responses in the greenhouse.

Resistance to herbicides inhibiting the biosynthesis of very‐long‐chain fatty acids

“…) . Resistance to triallate has evolved in Avena fatua L., selected in most of the fields where triallate has been used continuously for approximately 10–15 years or longer . Well documented are cases of resistance in the Echinochloa complex ( E. crus‐galli , E. oryzoides and E. phyllopogon ).…”

“…In Canada, resistance to the group N herbicides was first documented in the 1990s, occurring in approximately 50% of non‐random seed samples collected from plants that escaped field treatments with triallate. Similar cases were also documented in the northern Great Plains of the United States .…”

“…26 Resistance to triallate has evolved in Avena fatua L., selected in most of the fields where triallate has been used continuously for approximately 10-15 years or longer. 27,28 Well documented are cases of resistance in the Echinochloa complex (E. crus-galli, E. oryzoides and E. phyllopogon). Species of the Echinochloa genus have evolved resistance to thiobencarb and molinate in rice-based systems after repeated long-term use, in particular where field flooding has been practised.…”

Impact of Biotic and Abiotic Stresses on the Competitive Ability of Multiple Herbicide Resistant Wild Oat (Avena fatua)

“…ACCase and ALS-inhibiting herbicides have been used to control A. fatua since the 1970s and 1980s, respectively. However, repeated use of these herbicides, as well as others such as triallate and difenzoquat, led to the evolution of herbicide resistant A. fatua populations in the 1980s and 1990s [19], [20], [21]. Recently, two A. fatua populations with resistance to multiple herbicides including triallate (emergence inhibitor), flucarbazone (ALS-inhibitor), imazamethabenz (ACCase-inhibitor), paraquat (membrane disruptor), and difenzoquat (membrane disruptor) were reported [22].…”

Plant Response to Herbicides

“…Avena fatua (wild oat) populations resistant to triallate were first documented in 1990 in Alberta (O'Donovan et al, 1994) and subsequently reported in Montana (Kern et al, 1996a). The resistant biotypes are unusual in this case, because they represent metabolic loss-of-function mutants.…”