Hazelnut hectarage is expanding in Oregon. Weed competition in young orchards can severely reduce the growth and survival of plants. New orchards replace crops, including grass seed fields, which often are infested with herbicide-resistant weeds, including Italian ryegrass. This research evaluated hazelnut tolerance to pronamide, pyroxasulfone, and S-metolachlor. Three multi-year field experiments were conducted at newly planted orchards in the Willamette Valley during 2019 and 2020. Treatments compared pyroxasulfone (0.24 kg ai ha–1), pronamide (2.3 kg ai ha–1), and S-metolachlor (1.39 kg ai ha–1) applied at the reference rate, and at 2× and 4× that rate, compared to weed-free check. Treatments were applied within 2 wk after the winter transplant and reapplied the following year. Hazelnuts showed a high tolerance to all herbicides tested, with negligible injury noted (<3%). No changes in leaf chlorophyll were noted, averaging 242, 179, and 225 mg m–2 on each study site. Tree growth was similar among treatments as measured by trunk cross-sectional area, canopy volume, and internode length. A separate study evaluated the control of Italian ryegrass. Pronamide and pyroxasulfone provide 100% control of Italian ryegrass, and weed dry weight was reduced by up to 79 % compared to the grower standard. This study documents that hazelnuts are tolerant to pronamide, pyroxasulfone, and S-metolachlor, and that these herbicides can improve weed management in young orchards.

A field study was conducted twice in Elizabeth, MS, at on-farm sites in 2010–11 and 2011–12, and twice in 2012–13 at Mississippi State University’s Delta Research and Extension Center in Stoneville, MS, to evaluate glyphosate-resistant (GR) Italian ryegrass control and crop response to fall treatments followed by postemergence herbicide treatments in winter and/or spring. Italian ryegrass was controlled ≥92% and 61% following S-metolachlor and tillage 77 d after fall treatments (DA-FT), respectively. S-metolachlor fall treatment provided 33% greater control than clethodim winter treatment at 21 d after winter treatments (DA-WT). Tillage fall treatment followed by (fb) clethodim winter treatment fb paraquat spring treatment provided similar control (93%) to treatments containing S-metolachlor fall treatment fb a winter or spring herbicide treatment (≥93%) 24 d after spring treatments (DA-ST). Greatest soybean and corn density and yield were also observed following programs containing S-metolachlor fall treatment. Sequential postemergence herbicide treatments were not required to increase corn and soybean density and yield when S-metolachlor was used as a fall treatment. Growers have the best opportunity to maximize GR Italian ryegrass control when S-metolachlor fb a winter or spring herbicide treatment is used.

The objective of this paper was to review the reproductive biology, herbicide-resistant (HR) biotypes, pollen-mediated gene flow (PMGF), and potential for transfer of alleles from HR to herbicide-susceptible grass weeds including barnyardgrass, creeping bentgrass, Italian ryegrass, johnsongrass, rigid (annual) ryegrass, and wild oats. The widespread occurrence of HR grass weeds is at least partly due to PMGF, particularly in obligate outcrossing species such as rigid ryegrass. Creeping bentgrass, a wind-pollinated turfgrass species, can efficiently disseminate herbicide resistance alleles via PMGF and movement of seeds and stolons. The genus Agrostis contains about 200 species, many of which are sexually compatible and produce naturally occurring hybrids and hybrids with species in the genus Polypogon. The self-incompatibility, extremely high outcrossing rate, and wind pollination in Italian ryegrass clearly point to PMGF as a major mechanism by which herbicide resistance alleles can spread across agricultural landscapes, resulting in abundant genetic variation within populations and low genetic differentiation among populations. Italian ryegrass can readily hybridize with perennial ryegrass and rigid ryegrass due to their similarity in chromosome numbers (2n = 14), resulting in interspecific gene exchange. Johnsongrass, barnyardgrass, and wild oats are self-pollinated species, so the potential for PMGF is relatively low and limited to short distances; however, seeds can easily shatter upon maturity before crop harvest, leading to wider dispersal. The occurrence of PMGF in reviewed grass weed species, even at a low rate, is greater than that of spontaneous mutations conferring herbicide resistance in weeds and thus can contribute to the spread of herbicide resistance alleles. This review indicates that the transfer of herbicide resistance alleles occurs under field conditions at varying levels depending on the grass weed species.

Lolium multiflorum, one of the most important temperate forage grasses in the world, is used in integrated crop-livestock systems and as a cover crop. However, it is also one of the main weeds in winter crops. The continuous use of glyphosate to manage this species has led to the selection of resistant biotypes (LOLMU-R), making it important to prevent the dispersal of these seeds. This study aimed to assess the recovery and germination of LOLMU-R that have passed through the digestive system of cattle. The experiments were carried out in metabolism cages, using a completely randomized design with six replications. The animals were given 12 112 seeds each, which were recovered from their faeces over a period of 6 days. Germination of the recovered seeds was assessed in a germination chamber and compared against a control (no animal passage). After germination, a glyphosate dose-response curve was constructed. The results obtained showed a total recovery of 1109 seeds (9.1%), with maximum recovery 2 days after ingestion, decreasing to almost zero on day 6. Germination declined linearly as a function of recovery time; however, 4 days after ingestion, germination potential was 18%. The dose-response curve proved the resistance of the recovered seeds. Cattle is a dispersal agent for LOLMU-R seeds, with animals requiring 7 days of quarantine before moving from one infested area to another.

An understanding of the processes involved in grazing behaviour is a prerequisite for the design of efficient grassland management systems. The purpose of managing the grazing process is to identify sward structures that can maximize animal forage daily intake and optimize grazing time. Our aim was to evaluate the effect of different grazing management strategies on foraging behaviour and herbage intake by sheep grazing Italian ryegrass under rotational stocking. The experiment was carried out in 2015 in southern Brazil. The experimental design was a randomized complete block with two grazing management strategies and four replicates. The grazing management treatments were a traditional rotational stocking (RT), with pre- and post-grazing sward heights of 25 and 5 cm, respectively, and a ‘Rotatinuous’ stocking (RN) with pre- and post-grazing sward heights of 18 and 11 cm, respectively. Male sheep with an average live weight of 32 ± 2.3 kg were used. As intended, the pre- and post-grazing sward heights were according to the treatments. The pre-grazing leaf/stem ratio of the Italian ryegrass pasture did not differ between treatments (P > 0.05) (~2.87), but the post-grazing leaf/stem ratio was greater (P < 0.001) in the RN than in the RT treatment (1.59 and 0.76, respectively). The percentage of the non-grazed area was greater (P < 0.01) in post-grazing for RN compared with RT treatment, with an average of 29.7% and 3.49%, respectively. Herbage nutritive value was greater for the RN than for the RT treatment, with greater CP and lower ADF and NDF contents. The total time spent grazing, ruminating and resting did not differ between treatments (P > 0.05), with averages of 439, 167 and 85 min, respectively. The bite rate, feeding stations per min and steps per min by sheep were greater (P < 0.05) in the RN than in the RT treatment. The grazing time per hour and the bite rate were greater (P < 0.05) in the afternoon than in the morning in both treatments. The daily herbage intake by sheep grazing Italian ryegrass was greater (P < 0.05) in the RN than in the RT treatment (843.7 and 707.8 g organic matter/sheep, respectively). Our study supports the idea that even though the grazing time was not affected by the grazing management strategies when the animal behaviour responses drive management targets, such as in ‘Rotatinuous’ stocking, the sheep herbage intake is maximized, and the grazing time is optimized.

Narrow-windrow burning has been a successful form of harvest weed seed control in Australian cropping systems, but little is known about the efficacy of narrow-windrow burning on weed seeds infesting U.S. cropping systems. An experiment was conducted using a high-fire kiln that exposed various grass and broadleaf weed seeds to temperatures of 200, 300, 400, 500, and 600 C for 20, 40, 60, and 80 s to determine the temperature and time needed to kill weed seeds. Weeds evaluated included Italian ryegrass, barnyardgrass, johnsongrass, sicklepod, Palmer amaranth, prickly sida, velvetleaf, pitted morningglory, and hemp sesbania. Two field experiments were also conducted over consecutive growing seasons, with the first experiment aimed at determining the amount of heat produced during burning of narrow windrows of soybean harvest residues (chaff and straw) and the effect of this heat on weed seed mortality. The second field experiment aimed to determine the effect of wind speed on the duration and intensity of burning narrow windrows of soybean harvest residues. Following exposure to the highest temperature and longest duration in the kiln, only sicklepod showed any survival (<1% average); however, in most cases, the seeds were completely destroyed (ash). A heat index of only 22,600 was needed to kill all seeds of Palmer amaranth, barnyardgrass, and Italian ryegrass. In the field, all seeds of the evaluated weed species were completely destroyed by narrow-windrow burning of 1.08 to 1.95 kg m−2 of soybean residues. The burn duration of the soybean harvest residues declined as wind speed increased. Findings from the kiln and field experiments show that complete kill is likely for weed seeds concentrated into narrow windrows of burned soybean residues. Given the low cost of implementation of narrow-windrow burning and the seed kill efficacy on various weed species, this strategy may be an attractive option for destroying weed seed.

Research was conducted to determine the potential for allelopathy to occur in pastures infested with bitter sneezeweed. Aqueous extracts of bitter sneezeweed leaves reduced alfalfa and Italian ryegrass seedling growth as much as 50% at concentrations of 0.5% (w/v). Leaf extracts were more phytotoxic than either stem or root extracts and seedling growth was reduced more than seed germination. Bitter sneezeweed tissue mixed in potting soil at concentrations as low as 0.3% w/w reduced alfalfa seedling numbers by 43%, plant height by 26%, and foliage dry matter production by 54% compared to plants cultured in soil without bitter sneezeweed leaf tissue. The potential concentration of bitter sneezeweed leaf material in soil in the pasture ecosystem was determined to be 0.5% w/v in the liquid phase and 0.2% w/w in the solid phase. Alfalfa seedling growth was reduced by 70% when germinating seed were placed under a bell jar with a potted mature bitter sneezeweed plant compared to control seedlings. A potential exists for bitter sneezeweed interference with developing alfalfa and Italian ryegrass seedlings following fall interseeding into pastures infested with bitter sneezeweed.

Soybean consultants from Arkansas, Louisiana, Mississippi, and Tennessee were surveyed by direct mail and by on-farm visits in fall 2011 to assess weed management practices and the prevalence of weed species in midsouth U.S. soybean. These consultants represented 15, 21, 5, and 10% of total soybean planted in Arkansas, Louisiana, Mississippi, and Tennessee, respectively, in 2011. Collectively, 93% of the total scouted area in these four states was planted with glyphosate-resistant (RR) soybean. The adoption of glufosinate-resistant (LL) soybean was greatest in Arkansas (12%), followed by Tennessee (4%), Mississippi (2%), and Louisiana (< 1%). Only 17% of the RR soybean was treated solely with glyphosate, compared with 35% of LL soybean treated solely with glufosinate. Across four states, average cost of herbicides in RR and LL soybean systems was US$78 and US$91 ha−1, respectively. Collectively across states, total scouted area under conventional tillage was 42%, stale seedbed was 37%, and no-tillage was 21%. Palmer amaranth and morningglories were the most problematic weeds in all four states. Additionally, barnyardgrass and horseweed were the third most problematic weeds of Arkansas and Tennessee, respectively, and Italian ryegrass was the third most problematic weed in Louisiana and Mississippi. Glyphosate-resistant Palmer amaranth infested fewer fields in Louisiana (16% of fields) than it did in the remaining three states (54% collectively). Average Palmer amaranth hand-weeding costs in the midsouth was US$59 ha−1. Three-fourths of the midsouth consultants stipulated the need for continued research and education focused on management of glyphosate-resistant and glyphosate-tolerant weed species.

Winter wheat is the predominant crop in Oklahoma, but winter annual grasses are becoming increasingly difficult to control. Summer crop rotations have not been generally adopted; it was decided, therefore, to use winter canola in a crop rotation. However, very little is known about how well herbicides used in canola production will control the winter annual grasses found in Oklahoma wheat fields. Thus, an experiment was conducted at three sites, and repeated the following year, to determine the efficacy of trifluralin, quizalofop, clethodim, and glyphosate in canola production. The weeds evaluated in the experiment were Italian ryegrass, feral cereal rye, and volunteer wheat, along with two varieties of canola: a glyphosate-resistant variety and a conventional variety. All herbicides effectively controlled volunteer wheat. Feral cereal rye and Italian ryegrass varied in response to the herbicide treatments. Trifluralin followed by (fb) quizalofop and glyphosate fb glyphosate were effective on all target species across locations. Effective control of grass weeds was obtained in both conventional and glyphosate-resistant winter canola. Most herbicide treatments improved canola yield over the nontreated check. This experiment demonstrates that Oklahoma wheat producers can effectively rotate to canola to use other herbicides for control of problematic grassy weeds.

During the winter feeding period in organic dairy production systems in the alpine and pre-alpine regions of Austria and its neighboring countries, maize silage is an energy-rich forage that is regularly included in grass-silage-based diets to improve the energy supply of the cows. Italian ryegrass (Lolium multiflorum Lam.) is also a high-energy fodder grass popular as forage for dairy cows, but it is rarely cultivated in Austrian organic agriculture. The two crops differ in their cultivation demands and characteristics. Italian ryegrass establishes rapidly and may reduce the risk of soil erosion. Italian ryegrass would be a beneficial addition to crop rotation, which is an essential tool in successful organic farming. In a 15-week feeding trial, Italian ryegrass silage and maize silage were fed to 22 lactating Holstein dairy cows. Organically produced Italian ryegrass silage and maize silage were included at a rate of 40% [of dry matter (DM)] in grass-silage-based mixed basal diets. The mixed basal diets were supplemented with modest amounts of additional concentrates (2.7–3.0 kg DM day−1). Owing to the higher energy content of maize silage as compared to Italian ryegrass silage, the maize diet provided more energy [6.3 MJ net energy for lactation (NEL) kg−1 DM] than the ryegrass diet (6.15 MJ NEL kg−1 DM). The protein supply of the maize diet and the ryegrass diet was intended to be equal, but in fact the protein content of the maize diet was significantly lower (122 g crude protein kg−1 DM) than that of the ryegrass diet (141 g kg−1 DM). When the maize diet was fed, feed intake, milk yield and milk protein content were significantly higher as compared to the ryegrass diet. Also, intake of crude protein was significantly lower when feeding the maize diet, and in combination with the higher milk protein yield, this enabled an efficiency of gross nitrogen (N) utilization as high as 0.304. This level of N efficiency can be considered as above average and was significantly and considerably higher than the level of 0.259 observed when the ryegrass diet was fed. Therefore, maize silage upholds its reputation as an ideal energy-rich component in grass-silage-based dairy cow diets.