Collection of multispectral imagery from an aerial sensor is a means to obtain plotlevel vegetation index (VI) values; however, postcapture image processing and analysis remains a challenge for small-plot researchers. An ArcGIS Pro workflow of two task items was developed with established routines and commands to extract plotlevel VI values (normalized difference VI [NDVI], ratio VI [RVI], and chlorophyll index-red edge [CI-RE]) from multispectral aerial imagery of small-plot turfgrass experiments. Users can access and download task items from the ArcGIS Online platform for use in ArcGIS Pro. The workflow standardizes processing of aerial imagery to ensure repeatability between sampling dates and across site locations. A guided workflow saves time with assigned commands, ultimately allowing users to obtain a table with plot descriptions and index values within a .csv file for statistical analysis.The workflow was used to analyze aerial imagery from a small-plot turfgrass research study evaluating herbicide effects on St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] grow-in. To compare methods, index values were extracted from the same aerial imagery by TurfScout, LLC and were obtained by handheld sensor. Index values from the three methods were correlated with visual percentage cover to determine sensitivity (i.e., the ability to detect differences) of the different methodologies. Index values collected by handheld sensor were more sensitive to visual cover than those extracted from aerial imagery. Index values extracted by TurfScout, LLC were generally more sensitive to visual percentage cover than the workflow extraction method, but both detected similar trends of increasing index values as percentage cover increased.
St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] is one of the most common turfgrass lawn species of warm-season climates. Like many turfgrasses, it is produced as sod. Weed control during sod production is problematic, due in part to intolerance of St. Augustinegrass to a range of useful turfgrass herbicides, and because the open canopy and growth-conducive conditions of sod production favor certain difficult-to-control weeds. Although those weeds are best preventatively controlled using preemergence herbicides, many preemergence herbicides also adversely affect vegetative propagation of turfgrasses. Field research was conducted at the Mississippi State University, near Starkville, Mississippi, USA, to evaluate the effects of dithiopyr, pendimethalin, prodiamine, liquid-and granular-applied oxadiazon, atrazine, S-metolachlor, atrazine + S-metolachlor, and indaziflam on St.Augustinegrass establishment from plugs. Plots (2.25 m 2 ) were planted with 10 plugs (225 cm 2 apiece), and preemergence herbicides were applied at standard use rates 1 day after planting. Visual estimates of percentage cover were collected weekly, and aerial imagery was collected weekly to biweekly. Visual cover and vegetation index data were regressed to estimate days to reach 50% maximum nontreated response. Liquid-applied oxadiazon and atrazine were the only treatments that did not increase days to reach 50% cover in both replication years. Dithiopyr, prodiamine, S-metolachlor, and indaziflam increased days to reach 50% cover in both replication years. The normalized difference vegetation index, ratio vegetation index, and chlorophyll index-red edge derived from an aerial sensor, detected similar, but fewer, treatment differences compared to estimated visual cover. INTRODUCTIONSt. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] is a commonly grown lawn grass in the southeastern Abbreviations: CIRE, chlorophyll index-red edge; NDVI, normalized difference vegetation index; RVI, ratio vegetation index.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Annual bluegrass (Poa annua L.) is a problematic weed in turfgrass that has evolved resistance to 12 different herbicide sites of action. The mitotic inhibiting herbicide pronamide has both pre-and postemergence activity on susceptible annual bluegrass populations, but on certain resistant populations, postemergence activity is hypothetically compromised due to lack of root uptake or due to an unknown foliar resistance mechanism. Spray droplet size may affect foliar and soil deposition of pronamide, thus potentially explaining variation in population control or differential shoot and root uptake. Greenhouse experiments were conducted to quantify pronamide, flazasulfuron, and pronamide + flazasulfuron (a common tank mixture) deposition on annual bluegrass as affected by spray-droplet size. Five droplet sizes (200, 400, 600, 800, and 1,000 μm) were sprayed in an enclosed spray chamber on two-to three-leaf stage annual bluegrass plants. Fluorescent dye was added to each treatment solution to quantify the effects of herbicide and spray droplet size on herbicide deposition. Results indicate that spray droplet size affects deposition of pronamide and flazasulfuron, applied alone and in combination, on annual bluegrass. The highest foliar deposition was produced with 400-μm spray droplets in pronamide treatments and with 200 μm spray droplets in flazasulfuron and pronamide + flazasulfuron treatments. The addition of flazasulfuron to pronamide did not affect herbicide deposition when compared with pronamide-alone treatments. Results suggest that 200-to 400-μm spray droplets are optimal for foliar deposition of pronamide. Alternatively, larger droplet sizes may facilitate better soil deposition of pronamide where root uptake is optimal.
The auxin-mimicking herbicide quinclorac controls crabgrass (Digitaria spp.) after emergence in cool-and warm-season turfgrass species. Quinclorac resistance has been confirmed in smooth [Digitaria ischaemum (Schreb.) Muhl.] and large crabgrass [Digitaria sanguinalis (L.) Scop.]. Two Mississippi smooth crabgrass populations have been confirmed as quinclorac-resistant. Field experiments were conducted to evaluate programmatic approaches to control one of these populations. Treatments
Preemergence herbicides reduce weed competition during turfgrass establishment, yet little is known regarding preemergence herbicide safety on plugged St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze]. Field research was conducted in 2019 to evaluate the effects of prodiamine, pendimethalin, liquid-and granularapplied oxadiazon, S-metolachlor, atrazine, atrazine + S-metolachlor, dithiopyr, and indaziflam on St. Augustinegrass grow-in. St. Augustinegrass was established vegetatively. Herbicides were applied one day after planting. Visual cover and multispectral reflectance (handheld and aerial) were collected weekly. Chlorophyll Index-Red Edge (CI-RE), Ratio Vegetation Index (RVI), and Normalized Difference Vegetation Index (NDVI) were calculated. Indaziflam, which is not labeled for St. Augustinegrass grow-in or sod production, was included as a treated check and increased days to reach 50% cover and maximum index values from handheld and aerial methods. Prodiamine increased days to reach 50% cover for all response variables except aerialderived CI-RE and RVI. Atrazine as well as granular-and liquid-applied oxadiazon did not increase time to reach 50% visual cover and maximum vegetation index responses relative to the nontreated.
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