Field research was conducted to evaluate plant growth-regulator efficacy for tall fescue growth and seedhead suppression applied using application placement equipment. Specially designed equipment outfitted with fluid application systems applies low-volume plant growth regulator directly on plant foliage, reducing opportunity for drift and visible application. Wet-blade mowers are equipped to apply plant growth regulators and mow in a single pass, whereas rotary-wick applicators simply wipe chemicals directly on uncut vegetation. Therefore, a wet-blade, rotary-wick, and broadcast sprayer system were chosen to apply imazapic at three rates (9, 35, and 53 g ai/ha), and a mefluidide + chlorsulfuron tank mix at 7 + 140 g ai/ha to tall fescue roadsides for vegetative growth and seedhead suppression. Experiments were conducted during the spring and summer of 2004 in central and western North Carolina. Tall fescue was slightly injured and discolored by all treatments but fully recovered by 2 mo after treatment. Imazapic suppressed new vegetative growth 3 mo after treatment compared with the nonmowed–nontreated control (16.1 cm of growth) and the mowed–nontreated control (21.1 cm) when applied with the rotary-wick applicator (8.5 cm) and broadcast sprayer (6.2 cm). However, differences in vegetative height primarily occurred when application placement equipment treatments were compared with nontreated vegetation as opposed to mowed–nontreated plants. Although mowed–nontreated and wet-blade–treated plots had more new vegetative growth, nonmowed–nontreated plots still consistently had the greatest vegetative height. Seedhead suppression ranged from 87 to 100% when compared with the nonmowed–nontreated control, with wet-blade treatments consistently providing the least-effective seedhead suppression. Overall, application placement equipment did not improve plant growth-regulator efficacy when compared with the foliar broadcast spray.
Saflufenacil, a pyrimidinedione herbicide, is used for contact and residual broadleaf weed control in various crops. Bioactivity of saflufenacil in soil was tested in greenhouse and laboratory studies on 29 soils representing a wide range of soil properties and geographic areas across the United States. A greenhouse bioassay method was developed using various concentrations of saflufenacil applied PPI to each soil. Whole canola plants were harvested 14 d after treatment, and fresh and dry weights were recorded. Nonlinear regression analysis was used to determine the effective saflufenacil doses for 50% (ED50,), 80% (ED80), and 90% (ED90) inhibition of total plant fresh weight. Bioactivity of saflufenacil in soil was strongly correlated to soil organic (R= 0.85) and humic matter (R= 0.81), and less correlated to cation exchange capacity (R= 0.49) and sand content (R= −0.32). Stepwise regression analysis indicated that organic matter was the major soil constituent controlling bioactivity in soil and could be used to predict the bioactivity of saflufenacil. Saflufenacil phytotoxicity was found to be dependent on soil property; therefore, efficacy and crop tolerance from PRE and PPI applications may vary based on soil organic matter content and texture classification.
Concern about pesticide losses from maintained turfgrass areas led us to examine the fate of the triazine herbicide simazine in turfgrass systems and, specifically, interactions between simazine binding to soil organic matter and biodegradation. Soil samples were removed from turfgrass systems of different ages, placed in microcosms, conditioned as sterile or nonsterile, and exposed to 14C‐simazine. At seven sampling intervals, the soil was extracted and 14C was separated into three pools; bound, extractable, and CO2 With sterilized surface soil (0–5 cm), 52, 70, and 71% of applied 14C‐simazine was bound to soil from the 4‐, 21‐, and 99‐yr‐old turfgrass systems, respectively, after 16 wk. With nonsterile conditions, biodegradation became dominant, as 60 to 80% of the 14C was recovered in the CO2 fraction and binding was held at ∼20%. Among all soils evaluated, bound 14C and 14CO2 production was lower in subsurface soil (5–15 cm) from the 4‐ and 21‐yr‐old turfgrass systems. 14C‐simazine disappearance time (DT50) values under nonsterile conditions ranged from 0.9 to 5.8 wk. Results indicate that turfgrass systems have a relatively low amount of simazine available for leaching as the systems age due to a large capacity for biodegradation and binding to organic matter.
Pesticide sorption by soil is among the most sensitive input parameters in many pesticide-leaching models. For many pesticides, organic matter is the most important soil constituent influencing pesticide sorption. Increased fertility, irrigation, and mowing associated with highly maintained turfgrass areas result in constant deposition of organic material, creating a soil system that can change drastically with time. Changes in soil characteristics could affect the environmental fate of pesticides applied to turfgrass systems of varying ages. Sorption characteristics of simazine andS-metolachlor were determined on five soils from bermudagrass systems of increasing ages (1, 4, 10, 21, and 99 yr) and compared to adjacent native pine and bare-ground areas. Surface soil (0 to 5 cm) and subsurface soil (5 to 15 cm) from all sites were air-dried and passed through a 4-mm sieve for separation from plant material. Using a batch-equilibrium method, sorption isotherms were determined for each soil. Data were fit to the Freundlich equation, andKd(soil sorption coefficient) andKoc(organic carbon sorption coefficient) values were determined. Sorption and soil system age were directly related to organic matter content in the soil. Sorption of both herbicides increased with age of the soil system and was greatest on the surface soil from the oldest bermudagrass soil system. Herbicide sorption decreased at greater soil depths with lower organic matter. Greater amount of14C–simazine sorbed to subsurface soil of the oldest turfgrass system compared to14C–S-metolachlor. Results indicate that as bermudagrass systems age and accumulate higher organic matter levels increased herbicide sorption may decrease the leaching potential and bioavailability of simazine andS-metolachlor.
Seashore paspalum (Paspalum vaginatum Swartz) is a warm-season grass capable of growing in the saline environments present in coastal areas of Florida (2). A major limitation of cultivating turfgrasses in the sandy soils of Florida is the destruction of roots by plant-parasitic nematodes (3). A survey was performed to determine the plant-parasitic nematodes associated with seashore paspalum. Sampling locations ranged from Daytona Beach to Miami Beach on the eastern coast and from Tampa to Naples on the western coast. Soil samples were taken during the spring and summer months of 2002 and 2003 from different golf courses and home lawns. In 2002, soil samples were taken from five golf courses (37 samples) and seven home lawns (17 samples). In the next year, three golf courses (23 samples) and 13 home lawns (34 samples) were sampled. Nematodes were extracted from 100 cm3 soil samples using a modified centrifugal-sugar flotation technique (1). Ten genera of plant-parasitic nematodes were present from the samples obtained from golf courses. In addition, two more plant-parasitic nematode genera were present in samples from home lawns. The genera most frequently detected were Hoplolaimus, Mesocriconema, Hemicriconemoides, and Helicotylenchus, which were found at 100, 100, 88, and 88% of the golf courses surveyed and at 75, 95, 70, and 85% of the home lawns sampled, respectively. Genera Xiphinema, Pratylenchus, and Tylenchorhynchus, were found in less than 30% of the golf courses and less than 45% of the home lawns sampled. Genera Peltamigratus and Hemicycliophora were associated with a low percentage of the home lawns. A moderately high frequency of the genus Belonolaimus present in soil samples from golf courses (50%) and home lawns (40%) was consistent for other grasses grown in sandy soils associated with coastal areas in Florida (4). Populations of the genera Belonolaimus, Hoplolaimus, Helicotylenchus, Trichodorus, Hemicriconemoides, and Mesocriconema were above the action threshold levels for bermudagrass used by the University of Florida Nematode Assay Laboratory. Genera Hoplolaimus, Belonolaimus, and Trichodorus were associated with irregular-shaped yellowing and declining turfgrass areas sampled in this survey. Large populations of Helicotylenchus spp. (>500 nematodes per 100 cm3 of soil) were often found associated with seashore paspalum. To our knowledge, this is the first report of plant-parasitic nematodes associated with seashore paspalum in Florida. References: (1) W. R. Jenkins. Plant Dis. Rep. 48:692, 1964. (2) J. Morton. Proc. Fla. State Hortic. Soc. 86:482, 1973. (3) V. G. Perry and H. Rhoades. Pages 144–149 in: Nematology in the Southern Region of the United States. Southern Cooperative Series Bull. 276, University of Arkansas Agric. Pub., Fayetteville, 1982. (4) R. T. Robbins and K. R. Barker. J. Nematol. 6:1, 1974.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.