Crop, Forage and Turfgrass Management最新文献

Foliar fungicides are available to suppress Diplodia ear rot (DER), caused by Stenocarpella maydis (Berk.) Sutton and Stenocarpella macrospora (Earle) Sutton) in corn (Zea mays L.), but previous research has indicated these fungicides have limited efficacy against the disease using traditional over-canopy application methods. In an effort to improve coverage within the canopy and potentially improve disease control of DER, experiments were conducted in 2020, 2021, and 2022 to examine the effect of ground-driven, in-canopy fungicide nozzle technology on DER severity and spray coverage on the ear leaf and ear of corn plants. Application methods included over-canopy nozzles, over-canopy + drop nozzles, and over-canopy + 360 Undercover nozzles. Within each application method, treatments consisted of a non-inoculated control, or were inoculated with a conidial suspension of S. maydis. The fungicides benzovindiflupyr + azoxystrobin + propiconazole and pydiflumetofen + azoxystrobin + propiconazole were applied within each application method to measure efficacy against DER. In all years, neither fungicide product nor application method reduced DER severity. No fungicide applications increased yield compared to the non-treated control. The addition of drop nozzles or 360 Undercover nozzles to traditional over-canopy nozzles increased spray coverage on the ear (P < 0.0001) compared to over-canopy nozzles alone.

Take-all root rot (TARR) is a detrimental disease of ultradwarf bermudagrass (Cynodon dactylon × Cynodon transvaalensis; UDB) putting greens frequently diagnosed where warm-season grasses are grown. Since this disease is largely aggregated and variable under field conditions, field research is difficult and often yields inconsistent results. Multiple pathogens have only recently been associated with this disease, so practical management solutions such as fungicide efficacy and fungicide application timing have not been thoroughly investigated. Therefore, the objectives of this research were to determine the influence of fungicide selection and fungicide application timing on take-all root rot management under field and greenhouse conditions. In general, fungicides from the quinone outside inhibitor and/or demethylation inhibitor chemical classes provided the greatest reduction in take-all root rot severity. Fungicide applications that were made when soil temperatures were between 77–86°F provided the greatest disease suppression. The in vivo greenhouse method developed in this research proved to be an efficient and consistent method to evaluate management practices such as fungicide efficacy on take-all root rot. This research improves our understanding of fungicide efficacy and fungicide application timing for take-all root rot management on ultradwarf bermudagrass.

Proper N fertilization and higher mowing heights are recommended to enhance rooting for greater turfgrass summer drought stress. To examine the effects of these primary cultural practices on centipedegrass [Eremochloa ophiuroides (Munro) Hack.] drought response in the mid-Southern United States, a study was conducted to evaluate four mowing heights (1, 2, 3 and 4 inches) and N fertilization versus no fertilization. During the study, roots were periodically harvested at upper (0–3 inches) and lower (3–6 inches) soil depths, and roots were analyzed for architecture which included root length (RL) and surface area (SA), and root weight (RW). In July, plant-soil cores were subjected to 36-day drought simulation under greenhouse conditions. All turfgrass exhibited a pattern of decreasing leaf quality as drought progressed with unfertilized treatments maintaining acceptable leaf color (≥5) for 19 days at 5.9 compared to 4.8 for fertilized centipedegrass regardless of mowing height. In the field, root architecture and biomass across all mowing heights, fertilities, and soil depths peaked at 883.9 inches, 35.6 in², and 5.8 grains for RL, SA, and RW, respectively, six weeks prior to drought simulation (WDPS) before declining to 740.5 inches, 29.6 in², and 4.9 grains at the initiation of the drought simulation. The inability of N fertility and mowing height to enhance root growth particularly from spring into summer indicates soil temperatures may be a factor in centipedegrass root growth and thus drought stress avoidance.

Sorghum [Sorghum bicolor (L.) Moench] is a resilient forage crop due to its drought tolerance and adaptation to low-N environments. Sorghum produces a cyanogenic glucoside called dhurrin. The breakdown of dhurrin leads to the release of hydrogen cyanide (HCN), which can cause cyanide toxicity in livestock. Dhurrin-free sorghum lines have been developed through chemical mutagenesis by mutagenizing the gene for the first enzyme, CYP79A1, in the biosynthetic pathway. The CYP79A1 mutation was bred into sorghum lines to create a dhurrin-free experimental hybrid. Grazing preference of ewes was assessed when allocated to the dhurrin-free hybrid and three commercial hybrids. Near isogenic lines (NIL), contrasting in dhurrin production, were also compared for grazing preference. Forage mass was measured before and after grazing to determine the amount of forage mass grazed by the ewes. An unmanned aerial vehicle (UAV) was flown to quantify changes in normalized difference vegetation index (NDVI) over time for each hybrid. The nutritive values of the hybrids were also evaluated. The dhurrin-free hybrid was grazed 19% and 13% more (p-value ≤ 0.05) in comparison to the commercial hybrids for the second and third grazing cycles in 2019 and 2020. The NIL Tx623 bmr6 CYP79A1, was grazed 20% more than Tx623 bmr6 in two grazing cycles in 2020. Remote sensing data showed a similar pattern with the dhurrin-free hybrid having the largest decline in NDVI for three grazing cycles in 2019. Nutritive value of the dhurrin-free hybrid was similar to the two hybrids with the brown midrib (bmr) trait.

‘KSUZ 0802’ zoysiagrass (Innovation zoysiagrass, Zoysia matrella × Z. japonica) is a new cultivar that provides a high-quality playing surface on golf course fairways and tees. However, seedheads produced in late spring disrupt the playing surface. The plant growth regulator (PGR) ethephon has produced variable results in prior studies in suppressing zoysiagrass seedheads, and information for KSUZ 0802 is lacking. A two-year field experiment was conducted from 2019–2021 in Manhattan, KS, to assess the performance of ethephon (Proxy) on seedhead suppression of KSUZ 0802 zoysiagrass. Treatments included ethephon applied in a single application at 5 fl. oz. 1000 ft⁻² on multiple dates between August and November. Seedhead suppression was determined by counting seedheads in late spring. Ethephon applied in September provided >60% seedhead suppression; however, when applied during other months, variations were large between the two study years. Applying ethephon when accumulated cooling degree days (68°F base) were <37 resulted in >70% seedhead suppression, except for application on September 25, 2019. Late August ethephon applications, despite achieving good seedhead suppression (ranging from 54 to 80%), caused transient yet commercially unacceptable injury to KSUZ 0802 in both years. Application timing affected turf quality in late spring as KSUZ 0802 with fewer seedheads had better quality post-mowing, but no effect on spring greenup was observed. Ethephon can be an effective PGR for seedhead suppression in KSUZ 0802 zoysiagrass. However, careful consideration of application timing is essential as applying ethephon in late summer or late autumn can produce undesirable results.

Warmer than normal late fall temperatures may change standard fall harvest management of alfalfa (Medicago sativa L.) in western Canada. The objective of this study was to evaluate the forage yield and nutritive value of three types of alfalfa cultivars under different harvest managements. A field experiment was conducted from 2013 to 2017 using rhizomatous type (RR), cv. AC Yellowhead (M. sativa subsp. falcata), tap root type (TR), cv. Equinox (ssp. sativa) and creeping root type (CR), cv. Spredor 4 alfalfa (ssp. sativa), at Melfort, SK, Canada. The five harvest treatments were two 1-cut systems (early July or late July) and three 2-cut systems (early July + early or late September, late July + late September). Total forage yield was greater in TR and CR alfalfa than RR alfalfa; however, RR alfalfa had higher total forage yield under dry growing conditions versus CR alfalfa. The three alfalfa cultivars had a similar response to 2-cut harvest managements. The first cut yield was affected by the timing of the second cut of the previous year with the early September harvest reducing yield more than the late September. Three alfalfa cultivars had similar crude protein (CP), total digestible nutrient (TDN), and acid detergent fiber (ADF) concentrations. There was a significant nutrient yield benefit of TR and CR alfalfa under a 2-cut system over the RR alfalfa. Although the prairie climate is warming, the findings suggest that a fall rest period until late September is recommended regardless of alfalfa types to maintain high hay yield over multiple years.

High deoxynivalenol (DON) levels in corn (Zea mays L.) is a grain quality issue for many growers in the US Great Lakes region. High DON levels can be attributed to the interaction of environment, pathogen (Fusarium spp. causing ear rot), and hybrid susceptibility. However, ear-feeding insects can provide easy access for fungal infection and increase DON accumulation, hence the evaluation of insect protection strategies such as hybrid insecticidal proteins is crucial. Field trials were conducted at four locations in Michigan to study the impact of hybrids insect protection trait on ear injury, ear rot infection, and DON levels. Fungicide application (prothioconazole at silking stage) was conducted at two locations and included non-treated control. Insect feeding incidence (IFI) and ear rot incidence (ERI) were correlated at three locations but were stronger at locations with environments not conducive to fungal growth soon after silking. Correlation between IFI and DON was observed only at locations with highest insect pressure. Hybrid with Vip3A protein reduced IFI by >70% at all locations but lowered DON concentration at one out of three tested locations compared to non-Vip3A hybrids. Fungicide application reduced ear rot severity at one of two locations but did not impact ERI or DON levels. Overall, results showed that ear-feeding by insects can lead to an increase in ear rot and DON levels, and use of hybrids with Vip3A protein can reduce DON levels especially under high insect pressure.

Overseeding of bermudagrass (Cynodon dactylon L.) with perennial ryegrass (Lolium perenne L.) is often performed to provide green cover of dormant warm-season turfgrass in the winter. Fraise mowing is a cultural practice that can be used to disrupt the soil surface and hasten establishment of overseeded perennial ryegrass. Research was conducted to determine the most effective timing of overseeding for perennial ryegrass establishment in Northeast Mississippi, and to compare fraise mowing with other common cultural practices performed to enhance overseeding establishment. Treatments included fraise mowing at two depths (0.3 or 0.6 inches), scalping to a height of 1 inch, or vertical mowing to a depth of 1 inch at three timings (mid-September, mid-October, and end-October) prior to seeding perennial ryegrass at 435 lb pure live seed acre⁻¹. Plots were evaluated weekly for turfgrass quality, visual perennial ryegrass cover, and total green cover with digital image analysis. Fraise mowing to a depth of 0.6 inches and scalping resulted in quicker perennial ryegrass establishment. Fraise mowing to a depth of 0.3 inches resulted in quicker perennial ryegrass establishment than both the untreated control and vertically mowed treatments. End-October fraise mowing resulted in the slowest establishment, as growing conditions were not favorable for perennial ryegrass growth. Although the mid-September and mid-October treatments provided the most rapid perennial ryegrass establishment, almost all seeding timings were visually similar by March 15th of the following year. Though fraise mowing temporarily causes an undesirable playing surface, more rapid perennial ryegrass establishment is afforded by restricting bermudagrass competition.