A herbicide resistance risk assessment for weeds in wheat and barley crops in New Zealand

Abstract

We estimated the risk of selecting for herbicide resistance in 101 weed species known to occur in wheat and barley crops on farms in New Zealand. A protocol was used that accounts for both the risk that different herbicides will select for resistance and each weed's propensity to develop herbicide resistance based on the number of cases worldwide. To provide context we documented current herbicide use patterns. Most weeds (55) were low-risk, 30 were medium-risk and 16 high-risk. The top ten scored weeds were Echinochloa crus-galli, Poa annua, Lolium multiflorum, Erigeron sumatrensis, Raphanus raphanistrum, Lolium perenne, Erigeron bonariensis, Avena fatua, Avena sterilis and Digitaria sanguinalis. Seven out of ten high-risk weeds were grasses. The most used herbicides were synthetic auxins, an enolpyruvylshikimate-phosphate synthase inhibitor, acetolactate synthase (ALS) inhibitors, carotenoid biosynthesis inhibitors, and long-chain fatty acid inhibitors. ALS-inhibitors were assessed as posing the greatest risk for more species than other modes-of-action. Despite pre-emergence herbicides being known to delay resistance, New Zealand farmers only applied flufenacet and terbuthlazine with high frequency. Based on our analysis, surveys for herbicideresistant species should focus on the high-risk species we identified. Farmer extension efforts in New Zealand should address resistance evolution in cropping weeds.

Resistance to post-emergent herbicides is becoming common for grass weeds on New Zealand wheat and barley farms

“…minor , and S . media [ 6 ]. Bromus catharticus was resistant to ALS-inhibiting herbicides in this study, a first globally [ 5 ], but identified as medium to low risk by Ngow et al [ 6 ].…”

“…Globally, herbicide resistance is common in arable crops such as wheat (344 cases and 83 species) and barley (87 cases, 47 species) [ 5 ]. Based on worldwide patterns of resistance, Ngow et al [ 6 ] identified 16 species with a high risk of developing resistance in New Zealand wheat and barley fields (eight were grasses Avena fatua L., A . sterilis L., Digitaria sanguinalis (L.) Scop., Echinochloa crus-galli (L.) P.…”

Influence of herbicides under biofertilizer application on fennel (Foeniculum vulgare) yield and quality with special reference to herbicide residues

“…Chemical control using herbicides is mostly favored as they offer efficient, cost-effective and reliable weed control contributing to high seed yields. Herbicides are generally providing a threefold to fourfold economic return compared to other weed control measures (Ngow et al 2020). Studies have shown that herbicide application effectively controls the weeds and can increase the seed yield by 43.2 to 86.9% (Voevodin andBorisenko 1981 andPatel et al 2017).…”

Herbicide Resistance of Centaurea cyanus L. in Poland in the Context of Its Management

“…Herbicides from these groups were commonly applied for weed control in wheat [5,48]. According to Ngow et al [49], synthetic auxins were used most frequently in weed control in cereals. However, despite their frequent use in cereals, active substances from this group cause relatively little resistance, and they are included in the group of medium risk resistance [41].…”

“…Florasulam (HRAC 2), tribenuron (HRAC 2) and aminopyralid (HRAC 4) were also often used by farmers. Diflufenican was one of the substances used most frequently in the research presented by Ngow et al as well [49]. Considering that ALS inhibitors are among the herbicides that are very prone to resistance selection, a reduction in their use is an important recommendation [4,41].…”