Ryegrass resistance to glyphosate and amitrole is becoming common in New Zealand vineyards

Abstract

The prevalence of herbicide resistance in ryegrass (Lolium spp.) in the wine-growing regions in New Zealand is poorly understood. Cases of glyphosate, glufosinate and amitrole-resistant ryegrass were documented in a few vineyards in New Zealand in 2013, but there have been no regional surveys for resistance. To address this knowledge gap, 106 vineyards were visited across the important New Zealand wine-growing regions of Marlborough and Waipara in late February 2021, and Hawke’s Bay and Gisborne in late February 2022, and seed samples from individual plants at each site surviving weed-control measures were collected. Ryegrass was found in more South Island (68%) than North Island (20%) vineyards. These seeds, and those from a susceptible ryegrass population were sown in marked rows into trays (10-20 seeds per herbicide) and grown in a glasshouse. When seedlings reached the 3-4 leaf stage, trays were sprayed at the highest recommended label rate of glyphosate. Samples with enough seed were also screened against additional herbicides, amitrole, glufosinate or clethodim. The results indicated 39% of the surveyed vineyards contained glyphosate-resistant ryegrass, with cases detected across all regions, including 58% of vineyards in Marlborough. Eleven of the 27 Marlborough vineyards screened contained amitrole-resistant ryegrass; six samples were also resistant to glyphosate. However, glufosinate and clethodim were still effective against ryegrass at the sites tested. Considering the levels of herbicide resistance to ryegrass observed in this study, growers should explore alternative weed-suppression measures, including tilling, cover-crops, grazing, mowing and the use of herbicides with different modes of action.

The Electric Spatula: Killing Weeds with Pulsed Microshocks from a Flat-Plate Electrode

“…For decades, herbicides have provided easy-to-use, cost-effective weed management, but now, consumer preference for chemical-free food [1][2][3], awareness of environmental impacts [4,5], increasing regulations restricting agrichemical use [6,7], and the increasing prevalence of herbicide resistance [8][9][10] are forcing changes to weed management strategies [11]. The emergence of agritechnologies incorporating automation, machine vision, and artificial intelligence [12][13][14][15] and the development of new techniques for weed destruction [11,16,17] offer alternatives that minimise or avoid the requirement for herbicides and avoid soil disturbance and can work effectively in high crop or crop-residue conditions.…”

Opportunities for Improving Herbicide Resistance Management Strategies across New Zealand’s Arable Sector

“…Over the last two decades, however, the number of discovered cases has increased more rapidly and almost quadrupled. HR weed populations are now also found in vineyards, turf, and horticultural crops [1,[4][5][6][7]. This suggests resistance is an emerging challenge for New Zealand's agricultural sector.…”

“…In Canterbury, resistance has been detected in Lolium perenne (perennial ryegrass), Avena fatua (common wild oats), and Lolium multiflorum (Italian ryegrass) [5,[9][10][11]. A randomised survey of 20 per cent of cropping farms in one Canterbury district identified HR ryegrass on roughly one-third of sampled paddocks, as well as resistance in several other weed species [7,12]. These surveys indicate that HR is already prevalent across New Zealand's agriculture, creating a growing need for effective management.…”