Wild Mustard (Sinapis arvensis) Competition and Control in Rain-Fed Spring Wheat (Triticum aestivum L.)

Wild mustard (Sinapis arvensis L.) is a weed that frequently infests spring wheat (Triticum aestivum L.) fields in Moscow province, Russia. It is an annual broad leaf weed, which is indigenous throughout most parts of the globe and one of the most competitive weeds of spring cereal crops. In southern Russia it is emerging as an important crop competitor. Field trials focusing on herbicide timing and efficacy on wild mustard control and spring wheat yield in the Moscow region, Kashira and Baribino districts. A PRE glyphosate application to wheat regardless of fall or spring application timing favorably suppressed wild mustard in 2018. Weeds were not controlled in 2019 with the earliest application timings of glyphosate because weeds emerged late. In comparing fall and spring application timings, the formulated combination of (iodosulfuron/mesosulfuron/antidote mefenpyr-diethyl) at both field rates provided 80% weed control for all application timings and locations, and also resulting in the greatest spring wheat grain yield. Overall, herbicide treatments performed greater when they were in the fall than during the spring. Based on POST herbicide application, tribenuron-methyl provided the greatest wild mustard suppression (75%) and also caused the highest reduction in wild mustard biomass (3.3 g), stem number (6), seed number (880) and germination percentage (33%). When wild mustard was approximately 32 weeds/m2 causedtotal wheat yield loss.

Evaluation of disease, yield and economics associated with fungicide timing in Canadian Western Red Spring wheat

Protection from fungal plant pathogens is key for optimizing the yield and quality of wheat (Triticum aestivum). However, current grower practices and historical research do not always align with respect to optimum fungicide timing to maximize disease control, yield, quality and profitability of Canadian Western Red Spring (CWRS) wheat. Six fungicide treatments were evaluated at eight site-years across Alberta in 2018 and 2019 to determine the optimum time for fungicide application. The treatments included early fungicide applications at BBCH 22-23 (herbicide timing), early to mid-season application at BBCH 30-32 (plant growth regulator timing), ‘traditional’ timing at BBCH 39-45 (flag leaf), and head timing at BBCH 61-63 (fusarium head blight timing), and were compared with a non-treated control. Yield responses to fungicide treatments occurred at 50% of the site-years when disease pressure was 32% higher than in non-responsive site-years. Responsive site-years were characterized by higher relative humidity (65.4 - 74.0%) and an average 273 mm of precipitation. At responsive site-years, McFadden leaf spot disease severity ratings were 50% greater in early August when fungicides were applied at BBCH 22-23 and 30-32 versus at BBCH 39-45. At responsive sites, yield and thousand-kernel weight were 9.3% and 5.2%, higher, respectively, for fungicide applications at BBCH 39-45 and BBCH 61-63 compared with fungicide applications at BBCH 22-23 and BBCH 30-32. The most economically beneficial practices were applications of propiconazole, benzovindiflupyr and azoxystrobin (Trivapro A+B) at BBCH 39-45 or prothioconazole and tebuconazole (Prosaro XTR) at BBCH 61-63 when environmental conditions were conducive for disease development.

Weed management practices in Argentina crops

Data from surveys are used to help quantitatively diagnose the relative importance of chemical and nonchemical management practices, identify weed problems, and provide potential solutions. However, to our knowledge, such surveys have not been conducted in Argentina. In 2016, advisors and crop producers from cropping areas across Argentina were surveyed through email with the objectives to identify the main weed species problems and assess the use of chemical and nonchemical weed management practices in different crop production areas in Argentina. Fleabane, pigweed, johnsongrass, fingergrass, goosegrass, barnyardgrass, and ryegrass were considered the most important weeds. More than 53% of the producers used only chemical options; 86% used chemical fallow (i.e., keeping weed free with chemical application); 62% used full herbicide rates; 46% used proper herbicide timing; 41% used multiple modes of action; and 32% used rotation of herbicide modes of action. The main nonchemical practices used were crop rotation (45%); avoiding seed production during (31%) and after (25%) the crop cycle; narrow row spacing (19%); and cultivars with greater competitive ability (18%). Less than 15% of the people surveyed used increased crop densities or altered date of sowing. There is a high dependence on chemical control in the main crops grown in Argentina. Extension efforts are needed to emphasize the importance of integrated weed management.

Evaluation of Herbicide Timings for Palmer Amaranth Control in a Stale Seedbed Sweetpotato Production System

Studies were conducted in a stale field production system in 2012 and 2013 to determine the effect of herbicide timing on Palmer amaranth control and ‘Covington’ sweetpotato yield and quality. Treatments consisted of flumioxazin at 72, 90, or 109 g ai ha−1applied 45 d before transplanting (DBT) or 1 DBT, or sequentially the same rate at 45 DBT followed by (fb) 1 DBT; flumioxazin 109 g ha−1applied 1 DBT fbS-metolachlor (800 g ai ha−1) at 0, 6 (± 1), or 10 d after treatment (DAT); flumioxazin at 72, 90, or 109 g ha−1plus clomazone (630 g ai ha−1) applied 45 DBT fbS-metolachlor (800 g ha−1) applied 10 DAT; and fomesafen alone at 280 g ai ha−1applied 45 DBT. Nontreated weed-free and weedy controls were included for comparison. Flumioxazin application time had a significant effect on Palmer amaranth control and sweetpotato yields, and the effect of flumioxazin rate was not significant. Treatments consisting of sequential application of flumioxazin 45 DBT fb 1 DBT or flumioxazin plus clomazone 45 DBT fbS-metolachlor 10 DAT provided the maximum Palmer amaranth control and sweetpotato yields (jumbo, No. 1, jumbo plus No. 1, marketable) among all treatments. Delayed flumioxazin application timings until 1 DBT allowed Palmer amaranth emergence on stale seedbeds and resulted only in 65, 62, 48, and 17% control at 14, 32, 68, and 109 DAT, respectively. POST transplantS-metolachlor applications following flumioxazin 1 DBT did not improve Palmer amaranth control, because the majority of Palmer amaranth emerged prior toS-metolachlor application. A control program consisting of flumioxazin 109 g ha−1plus clomazone 630 g ha−1at 45 DBT fbS-metolachlor 800 g ha−1at 0 to 10 DAT provides an effective herbicide program for Palmer amaranth control in stale seedbed production systems in North Carolina sweetpotato.

Weed Ecology and Weed Management Strategies for Dry-Seeded Rice in Asia

Rice is a principal source of food for more than half of the world population, and more than 90% of rice worldwide is grown and consumed in Asia. A change in establishment method from manual transplanting of rice seedlings to dry-seeded rice (DSR) has occurred in some countries as growers respond to increased costs or decreased availability of labor or water. However, weeds are a major constraint to DSR production because of the absence of the size differential between the crop and the weeds and the suppressive effect of standing water on weed growth at crop establishment. Herbicides are used to control weeds in DSR, but because of concerns about the evolution of herbicide resistance and a scarcity of new and effective herbicides, there is a need to integrate other weed management strategies with herbicide use. In addition, because of the variability in the growth habit of weeds, any single method of weed control cannot provide effective and season-long control in DSR. Various weed management approaches need to be integrated to achieve effective, sustainable, and long-term weed control in DSR. These approaches may include tillage systems; the use of crop residue; the use of weed-competitive cultivars with high-yield potential; appropriate water depth and duration; appropriate agronomic practices, such as row spacing and seeding rates; manual or mechanical weeding; and appropriate herbicide timing, rotation, and combination. This article aims to provide a logical perspective of what can be done to improve weed management strategies in DSR.

Cover crops and herbicide timing management on soybean yield under no-tillage system

The objective of this work was to evaluate the effect of cover crops and timing of pre-emergence herbicide applications on soybean yield under no-tillage system. The experiment consisted of four cover crops (Panicum maximum, Urochloa ruziziensis, U. brizantha, and pearl millet) and fallow, in addition to four herbicide timings (30, 20, 10, and 0 days before soybean sowing), under no-tillage system (NTS), and of two control treatments under conventional tillage system (CTS). The experimental design was a completely randomized block, in a split-plot arrangement, with three replicates. Soybean under fallow, P. maximum, U. ruziziensis, U. brizantha, and pearl millet in the NTS and soybean under U. brizantha in the CTS did not differ significantly regarding yield. Soybean under fallow in the CTS significantly reduced yield when compared to the other treatments. The amount of straw on soil surface did not significantly affect soybean yield. Chemical management of P. maximum and U. brizantha near the soybean sowing date causes significant damage in soybean yield. However, herbicide timing in fallow, U. ruziziensis, and pearl millet does not affect soybean yield.

Herbicide Timing and Rate Effects on Weed Management in Three Herbicide-Resistant Canola Systems

Herbicide-resistant canola dominates the canola market in Canada. A multiyear field experiment was conducted at three locations to investigate the effect of time of weed removal (two-, four-, or six-leaf canola) and herbicide rate (50 or 100% recommended) in three herbicide-resistant canola systems. Weeds were controlled in glufosinate-resistant canola (GLU) with glufosinate, in glyphosate-resistant canola (GLY) with glyphosate, and in imidazolinone-resistant canola (IMI) with a 50:50 mixture of imazamox and imazethapyr. Canola yields were similar among the three canola cultivar–herbicide systems. Yields were not influenced by 50 vs. 100% herbicide rates. Timing of weed removal had the greatest effect on canola yield, with weed removal at the four-leaf stage giving the highest yields in most cases. Percent dockage was often greater for GLU and IMI than for GLY. In comparison with the other treatments, dockage levels doubled for GLU after application at 50% herbicide rates. The consistency of monocot weed control was usually greater for GLY than for GLU or IMI systems. However, weed biomass data revealed no differences in dicot weed control consistency between IMI and GLY systems. Greater dockage and weed biomass variability after weed removal at the six-leaf stage or after low herbicide rates suggests higher weed seed production, which could constrain the adoption of integrated weed management practices in subsequent years.