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weeds and seeds banff

Weeds and seeds banff

Weed control programs that use herbicides have proven to be cost-effective for improving yields of staple crops by an average of 30% [1], and typically provide a 2-4-fold economic return [2]. They are also a key element in no-till planting programs for wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) farms in New Zealand that improve soil structure and prevent soil loss through erosion [3]. Nevertheless, farmer practices worldwide have led to the selection of weeds with infrequent genetic mutations that confer resistance to the herbicides, allowing weeds to escape control, reproduce and form resistant populations [4]. 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. Beauv., Lolium multiflorum Lam., L. perenne L., Phalaris minor Retz., and Poa annua L.; these grasses were in the top 10 for risk of developing herbicide resistance).


We also report results from a few other weeds supplied to us by industry agronomists that were tested. S. media samples were sourced from ryegrass rotation (near Matamata on the North Island) and one sample from Ashburton in the South Island from a field planted in clover and ryegrass were treated with flumetsulam 30 g ai/ha (Preside ® ) and a paraffinic oil surfactant (0.5%), and chlorsulfuron 20 g ai/ha (AgPro Chloro ® ) with a non-ionic surfactant (0.25%). D. sanguinalis supplied to us from two maize (Zea mays L.) farms near Matamata on the North Island was treated with nicosulfuron 60 g ai/ha with paraffinic oil surfactant (0.5%) (S1 Appendix).

Table 1

This study is the first random survey carried out in New Zealand to detect herbicide resistance for a range of arable weeds and estimate its prevalence on wheat and barley farms. Such surveys may not have been implemented previously because costs of these investigations are prohibitive, an earlier estimate suggested it could cost as much as 759 NZD (New Zealand Dollars) per farm [27]. However, we estimated costs of approximately 370 NZD per farm in the second year of these surveys. After randomly sampling of >20% wheat and barley farms in the targeted regions, resistance was detected in 48% of the sampled farms, this is likely to be lower than the true rate since detection is imperfect [27]. The basis for this argument is that we could have missed individual resistant plants in a field and because we focused on up to ten plants in just two fields per farm, depending on which weeds were available to collectors prior to harvest [18,19]. Our sampling rate is better suited to the detection of outcrossing weed species but could miss some self-pollinating species [18,19]. Species previously identified as having an elevated risk of developing herbicide resistance in wheat and barley fields were confirmed resistant, i.e., L. multiflorum, L. perenne, A. fatua, P. 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].

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Date and time: Fri, 14 Jan 2022 08:02:26 GMT

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