Preemergence herbicides are generally considered as a group to negatively affect hybrid bermudagrass (Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy) establishment. However, little is known about the effects upon hybrid bermudagrass root growth, establishment, and sod harvestability. Several research projects were conducted at Mississippi State University to determine the effects of commonly used preemergence herbicides on hybrid bermudagrass sod production. Measured response variables included visually estimated hybrid bermudagrass cover, normalized difference vegetative index (NDVI), ratio vegetative index (RVI), relative chlorophyll concentration (CI-RE), sod tensile strength, root mass, root length, root surface area, average root diameter, and root carbohydrate concentration after application of these herbicides. While several of these preemergence herbicides initially reduced hybrid bermudagrass growth, hybrid bermudagrass was generally able to recover and outgrow the herbicidal effects by the end of the growing season.

White clover (Trifolium repens) is a common and difficult weed to control in turfgrass as it is a highly visible and unsightly weed that disrupts the uniformity of the turfgrass surface. This weed is a serious problem in the turfgrass industry in California and there is a need for better methods of control. With more regulations on pesticides and less information about efficient application techniques, controlling white clover with available herbicides can be difficult. Compatibility trials were conducted during the summer of 2005 to determine the compatibility of the herbicides and adjuvants planned for use in subsequent greenhouse and field trials. A greenhouse trial was conducted in the spring of 2006, followed by field trials in fall of 2006 and spring of 2007 to determine the efficacy of two herbicides on white clover when combined with each of three adjuvants and two nozzles. Results showed the nozzles to have no significant effect on phytotoxicity to white clover in the greenhouse trial, while some of the herbicides and adjuvants significantly increased phytotoxicity to white clover. In the field trials, adjuvants had no effect on phytotoxicity, while some herbicides and nozzles significantly increased phytotoxicity to white clover, perennial ryegrass and common bermudagrass. Information about the combination of herbicides, adjuvants and nozzles will help turfgrass managers to improve their management of white clover in turfgrass.

Winter injury of bermudagrass (Cynodon spp.) continues to be a problem across the transition zone. In an attempt to delay or induce winter dormancy while maintaining cold hardiness, applications of seaweed extract (SWE) (0.54 kg ha-1), ethephon (16 L ha-1), Fe (1 kg ha-1), and N (49 kg ha-1) took place every three weeks during the fall of 2001 and 2002. Cultivars examined included 'Riviera', 'Midiron', 'Princess', and 'Tifway'. Tifway exhibited greatest fall color retention in both years of the study. Ethephon promoted early senescence and turfgrass quality during fall ratings in both years of the study while N, Fe, and SWE increased quality over the control in 2001 and only N showed better quality and color retention over the control in 2002. Samples removed from cold acclimated plots were artificially frozen as a measure of cold hardiness. Treatments did not have an effect on post freeze regrowth, however, cultivar was significant in both years. Midiron showed best regrowth followed by Riviera, Tifway, and Princess. In both years Riviera and Midiron displayed the quickest and greatest amount of spring greenup followed by Tifway and then Princess. Ethephon reduced greenup in both years and SWE, Fe, and N showed no differences from the control in 2001 and Fe showed significantly better greenup in 2002. Proline and Linolenic acid levels were highest in Midiron, followed by Riviera, Tifway, and Princess. Nitrogen, SWE, and Fe generally did not have an effect on linolenic acid and no consistent effects were noted on proline concentration. Ethephon treatments did not have an effect on linolenic acid levels, however, there was a negative effect on proline concentrations. The results of this study indicate that judicial N applications during the fall can promote color retention and do not have a negative effect on bermudagrass cold-tolerance. Linolenic acid and proline findings also help to explain differences in cold-tolerance between different bermudagrass cultivars. / Ph. D.

This research addressed the identification and distribution of selected ERI fungi within two greens at Mississippi State University Golf Institute using novel molecular methods, spatial relationships of fungal distribution and turf health assessments, and fungal sensitivity to selected fungicides. A complex of ERI fungi was identified in both greens. Gaeumannomyces graminis, Gaeumannomyces sp., and Candidacolonium cynodontis were randomly distributed based on spatial autocorrelation in both green samplings, while Magnaporthiopsis cynodontis clustered in Green 2 for both samplings and in Green 12 of the 2018 sampling. Clustering of turf health values was variable by month in each green, and no spatial relationship was determined between turf health values and fungal presence. Five ERI fungal isolates were exposed to four fungicide classes with relative growth present at 100 ppm. The EC50 values for the selected fungi ranged from 2.33 to >100 ppm and suggests a lack of sensitivity to the selected fungicides.

Shelf-life and transplantation success of sodded and sprigged turfgrasses are negatively affected by disruptive harvest techniques and post-harvest handling/storage conditions. Air and light are limited inside of stacked pallets of sod or masses of sprigs/plugs, which triggers multiple processes that may lead to poor transplant success. Current research looks at the effects of several commercially available turfgrass products and cultural practices on post-harvest bermudagrass storage, its grow-in after transplantation, and harvested area recovery. Ensilation and internal heating sometimes observed in stored, full-sized pallets of sod were difficult to simulate in small-size sod masses. When storage environment and post-harvest conditions were controlled, refrigeration of stored bermudagrass slowed establishment, which is contrary to common knowledge and industry practice. Fluxapyroxad + pyraclostrobin fungicide positively affected turfgrass grow-in during field and greenhouse experiments, and in some instances hastened growth and recovery of bermudagrass.

Bermudagrass (Cynodon dactylon (L.) Pers.) is a popular turfgrass used throughout the Southeast. Bermudagrass is established primarily as sprigs on large acreage sites. Currently, the industry standard practice (ISP) of fertilization during bermudagrass sprig establishment is 48.8 kg N ha⁻¹ wk⁻¹. This fertilizer rate can be excessive on morphologically immature sprigs in the initial weeks of establishment, thus making the possibility of offsite surface runoff N events more likely. Two experiments were conducted in 2000 and 2001 where sprigs were established at 2, 4, 6, 8, and 10 weeks prior to applying simulated rainfall (WPRS) following N fertilization rates of the ISP or a lower initial N (LIN) rate of 12.2 kg N ha⁻¹ wk⁻¹ the first four weeks and then 48.8 kg N ha⁻¹ wk⁻¹ until full establishment. At the tenth week all treatments were subjected to rainfall simulation at 63.5 mm hr⁻¹. Once surface runoff was induced, rainfall continued for thirty minutes during which time runoff samples were taken every five minutes and analyzed for sediment losses, N concentrations in the nitrate and ammonium forms, and phosphorus losses as dissolved reactive P (DRP). Experimental results indicate an ability to curb N losses through surface runoff during the initial weeks of sprig establishment following the LIN with only modest delays in sprig establishment. Sprigs established for the same time period, under the ISP or LIN, were very similar in growth, release of surface runoff, and sediment losses during runoff events. / Master of Science

AuxiGro® WP was evaluated for effects on bermudagrass seed production in the Palo Verde Valley of far eastern California. Four rates of this product, in addition to a 4 oz./acre rate with two fertilizers were tested, as were the fertilizers only to separate treatment effects. Highest yields from subplot harvests were noted from the 2 and 4 oz./acre rates of AuxiGro® WP, and germination percentages from these treatments and resultant pure live seed were also numerically higher (81-99 lbs./acre) than that noted from untreated bermudagrass, although most plant parameters did not result in statistical difference.

Usage of gibberellic acid inhibitors have been documented to increase seed harvest of grasses in the Pacific Northwest, but had not been evaluated for bermudagrass seed production in the low desert. Four rates of PalisadeTM (1-4 pts/acre)and three rates of Apogee7 (7-29 oz) were applied to 'Cheyenne' bermudagrass (Cynodon dactylon) to evaluate their effects on seed production. Treatments were applied just prior to inflorescence appearance, and lowest two rates of both chemistries included both single as well as double applications with second application approximately two weeks after experiment initiation. All PalisadeTM treatments significantly reduced plant heights and inflorescence heights, as did twice applied Apogee7 treatments for plant heights. Most PalisadeTM treatments also significantly reduced total inflorescence length as well as opened 'heads'. Data indicate that higher rates of both chemistries and especially PalisadeTM significantly reduced seeds per unit area. Of the treatments, only the lowest rate of Apogee7 (1 pt/acre) resulted in a numeric increase of seeds/acre compared with the untreated check.

Two rates of the insect active ingredient zetacypermethrin (MustangMax) were evaluated for control of summer insect pests on bermudagrass, with application made about one month prior to harvest. Crop was 22 inches tall when treatments were applied and had a dense stand, which also intercepted much of the treatment. Little difference existed between the two rates of zetacypermethrin in this study. Treatments reduced planthopper numbers by slightly over 50% for the first 9 days after application. Reduction of bermudagrass mirid populations was 45% at two days post treatment, but numbers of this insect were numerically higher in MustangMax treated plants than in untreated plots at subsequent sample dates. Treatments also resulted in significantly lower numbers of damsel bugs and minute pirate bugs at two days post treatment, while only reducing grass thrips numbers by about 20% through 13 days after application. Bark lice were more prevalent in the treated plots, thought due to a reduction of predatory beneficial insects. More effectiveness from this chemistry would be expected earlier in the growing season when plants are shorter, therefore allowing greater coverage and contact with insects as this chemistry is not systemic.

This study was conducted to determine the effect of forage CP level on intake and digestion of Coastal bermudagrass hay by horses. Four cecally fistulated geldings were used in a 4 x 4 Latin square design with four treatments and four periods. Horses were fed one of four Coastal bermudagrass hays consisting of 7, 10, 13, or 16% CP during each of the 4 15-d periods. Intake and apparent digestibility were determined for each horse at the end of each period by total fecal collection. In addition, cecal fluid and blood samples were collected from each horse on the last day of each period for determination of cecal ammonia, cecal pH, plasma urea nitrogen, and plasma glucose concentrations. Crude protein concentration of Coastal bermudagrass hay influenced equine intake and digestion. Increasing CP concentration linearly increased digestible OM intake (DOMI) from 3.79 to 5.98 kg/d for 7 and 16% CP hay, respectively (P = 0.04). Furthermore, as forage CP level increased, CP intake increased linearly (P < 0.01). Forage CP level had no effect on forage DM intake. Quadratic effects (P less than or equal to 0.05) were observed for forage OM, NDF, ADF, and digestible energy. Overall digestibility was lowest for the 7% CP hay and highest for the 10% CP hay. Cecal pH remained above 6.62 irrespective of treatment and time, indicating that cecal pH was suitable for microbial growth. As forage CP level increased, cecal ammonia concentration increased linearly from 0.03 mM for the 7% to 1.74 mM for the 15% CP hay (P < 0.01). Concentration of plasma glucose also linearly increased (P = 0.04) from 68.77 to 73.68 mg/dL as CP concentration increased from 7% to 16% CP. Plasma urea nitrogen exhibited a quadratic effect as concentration increased (P < 0.01) from 4.34 to 5.61 mM for the 7 and 16% CP hays, respectively.