One method of plant freeze protection involves the application of compounds that promote freeze avoidance or tolerance. FreezePruf, a commercially available product recently marketed to improve both freeze avoidance and tolerance, contains polyethylene glycol, potassium silicate, glycerol, silicone polyether surfactant, and a bicyclic oxazolidine antidessicant. The goal of the present study was to evaluate the protection level provided by FreezePruf using laboratory-based methods involving plants and plant parts from species capable and incapable of low-temperature acclimation. FreezePruf did not lower the freezing temperature of pepper (Capsicum annuum) seedlings, celosia (Celosia argentea) seedlings, detached tomato (Solanum lycopersicum) leaves, or postharvest tomato fruit. Spray application of the putative cryoprotectant did not increase the freeze tolerance of bermudagrass (Cynodon dactylon) crowns or stolons. It is possible that a greater level of protection could be achieved with other species or different experimental protocols.
R.N. Carrow and B.J. Johnson
A turfgrass wear injury study was conducted at Griffin, Ga., on `Tifway' bermudagrass (Cynodon dactylon × C. transvaalensis) using two golf car tires and three golf car types driven in a semicircular pattern to deliver 85 passes over the tread path plot area. Wear injury for the 14 days after wear was applied was assessed by visual quality, percent green coverage, leaf bruising, and verdure. Golf tire × car interactions occurred, but more wear occurred with the low pressure (48 × 103 Pa), dimpled tread tire with flexible sidewalls than the commonly used bias ply (4-ply), V-shaped tread tire with more rigid sidewalls. Significant differences in wear damage occurred for golf car type but were influenced by tire design. Thus, selection of golf car tire and golf car type can influence the degree of wear injury on turfgrass sites.
J.L. Nus and K. Shashikumar
Although the effect of cold winters on the severity of bermudagrass (Cynodon dactylon Pers.) spring dead spot (SDS) has been studied, information is needed concerning the effect of infection by fungi associated with SDS on the host's freezing resistance. A-22 bermudagrass was inoculated with Leptosphaeria korrae J. Walker & A.M. Smith and Ophiospharella herpotricha (Fr.) J. Walker & A.M Smith. Differential thermal analysis was used to monitor exotherm temperatures of healthy and O. herpotricha- and L. korrae-infected A-22 bermudagrass at 10-day intervals during 90 days of acclimation in cold chambers. Healthy bermudagrass crowns supercooled to an average of -6.7C and fungi-infected crowns supercooled to an average of -4.8 and -4.4C, respectively. Healthy crown exotherm temperatures were significantly lower than those of fungi-infected bermudagrass crowns on all nine sampling dates. This result indicates that fungi-infected plants are more susceptible to cold damage.
The usefulness of cover crops for weed management in strawberries were evaluated. Wheat (Triticum aestevum L.), rye (Secale cereale L.), and crimson clover (Trifolium incarnatum L.) were grown in individual pots then killed by tillage or herbicide and followed in the same pots by plantings of bermuda grass [Cynodon dactylon (L.) Pers.], yellow nutsedge (Cyperus esculentus L.), crabgrass [Digitaria ischaemum (Schreb.) Schreb. ex Muhl.], or strawberries (Fragaria ×ananassa `Cardinal'). Rye and wheat tilled into the medium generally increased the growth of strawberries and decreased the growth of bermuda grass. Rye and wheat residues appeared to suppress growth of weeds and strawberries when the residues remained on the medium surface. Crimson clover had little affect on the growth of weeds or strawberries. Yellow nutsedge and crabgrass were not significantly affected by cover crop residues.
Glyphosate traditionally has been used by growers and landscapers as a nonselective herbicide; however, selective uses do exist. The use of glyphosate to control weeds in dormant and actively growing bermudagrass (Cynodon dactylon) is an example of selective weed control. Several ornamentals, including conifer species, have been known to exhibit good tolerance to over-the-top applications of glyphosate. Unfortunately, little published information exists on rates of glyphosate that may be used on specific ornamental species. The objective of this research was to determine the tolerance levels of three juniper species [‘Blue Pacific’ shore juniper (Juniperus conferta), ‘Blue Star’ juniper (Juniperus squamata), and ‘Parsoni’ juniper (Juniperus davurica)] to various rates of glyphosate. Research conducted in 2004 and 2005 indicated that injury to three juniper species did not exceed 23% with glyphosate rates up to 2.5 lb/acre.
Michael T. Deaton and David W. Williams
Common bermudagrass (Cynodon dactylon) and hybrid bermudagrass (Cynodon dactylon var. dactylon × C. transvaalensis) often are used for athletic fields as a result of their wear tolerance and recuperative ability. A wear tolerance study was conducted May 2007 through Nov. 2008 in Lexington, KY. Plots were managed as athletic turf and simulated traffic was applied during the Kentucky high school football seasons. The cultivars Quickstand, Tifway 419, Riviera, and Yukon grown in a sand-based medium were evaluated. Trinexapac-ethyl (TE) was applied at label rates and frequencies or left untreated. Overseeding treatments were perennial ryegrass (Lolium perenne) at 0, 546, and 1093 lb/acre pure live seed. Traffic treatments were applied with a Brinkman traffic simulator three times per week, once each Monday, Wednesday, and Friday, without regard to soil moisture status or weather for the periods 10 Sept. to 2 Nov. 2007 and 12 Sept. to 14 Nov. 2008. In both years of the study, the main effect of cultivar was significant (P < 0.05) in traffic tolerance (‘Tifway 419’ = ‘Riviera’ > ‘Quickstand’ = ‘Yukon’). Overseeding at the medium and high rates also provided significantly greater turf cover for the coarse-textured, more open cultivars (Quickstand and Yukon) over the fine-textured, more dense cultivars (Riviera and Tifway 419). Applications of TE did not significantly improve tolerance to simulated athletic traffic in either year of the study regardless of cultivar or overseeding treatment. Within the parameters of this study, data indicate that only cultivar has significant effects on tolerance to simulated traffic on a sand-based field. Overseeding treatments for the fine-textured, more dense cultivars and TE applications on sand-based field systems had no positive significant effects on tolerance to simulated traffic.
James N. McCrimmon
Limited information is available concerning the mineral nutrient content of different turfgrass species. There is a need to develop sufficiency ranges for turfgrasses under various management programs. The nutrient concentration of a turfgrass provides an indication of the nutrient status and quality of the turf. A study was conducted to assess the mineral nutrient composition of selected turfgrass species and cultivars. Plant tissue samples of the following turfgrasses were collected: creeping bentgrass, Agrostis palustris Huds. `Penncross'; bermudagrass, Cynodon dactylon (L.) Pers. `NuMex Sahara', `Santa Ana', `Texturf 10', and Cynodon dactylon (L.) Pers. × Cynodon transvaalensis Burtt-Davy `Tifgreen', `Tifway'; perennial ryegrass, Lolium perenne L. `Medalist × Blend'; St. Augustinegrass Stenotaphrum secundatum (Walt.) Kuntze `Seville'; and zoysiagrass, Zoysia japonica Steud. `El Toro' and Zoysia japonica × Zoysia tenuifolia Willd. ex Trin. `Emerald'. Three samples of each cultivar were collected, washed with deionized water for 30 s, and dried in a forced-air oven at 70°C for 72 hr. Plant samples were analyzed for both macronutrient and micronutrient concentration. For the bermudagrass cultivars, the concentrations of potassium (K) and magnesium (Mg) were less than 20.0 g·kg-1 and 2.0 g·kg–1, respectively, and less than known sufficiency levels. `Tifway' and `Texturf 10' had lower nitrogen (N) concentrations than other bermudagrasses. `Penncross' and `Medalist X' had the highest N concentrations. Zoysiagrass had low concentrations of N, phosphorus (P), calcium (Ca), K, and Mg. The concentration of copper (Cu) was low for zoysiagrass and three bermudagrass cultivars (`Texturf 10', `Tifgreen', and `Tifway'). There were differences among the turfgrasses for manganese (Mn) and zinc (Zn) concentrations.
Hassan Salehi, Zahra Seddighi, Alexandra N. Kravchenko, and Mariam B. Sticklen
Bermudagrass (Cynodon L.C. Rich.) is grown on more than 4 million ha in the southern United States. The black cutworm (Agrotis ipsilon Hufnagel) is the most commonly encountered pest of bermudagrass, especially on golf course greens. Developing insect-resistant cultivars is a very desirable substitute, both environmentally and economically, to using current synthetic pesticides. Here we report, for the first time, Agrobacterium-mediated transformation of `Arizona Common' common bermudagrass [Cynodon dactylon (L.) Pers.] with the Bacillus thuringiensis Berliner cry1Ac gene encoding an endotoxin active against black cutworm. Mature seeds were used for producing embryogenic callus, and calli were transformed with a plasmid containing a synthetic cry1Ac and the kanamycin resistance (nptII) genes. Putative transgenic calli and plantlets were selected on media containing 100 and 50 mg·L-1 G418, respectively. RNA-blot analysis of PCR-positive lines revealed the expression of the cry1Ac transgene in three out of five putative transgenic lines. The larvae fed on transgenic plant leaves experienced highly significant (over 80%) mortality.
Jennifer M. Johnson-Cicalese and C.R. Funk
Studies were conducted on the host plants of four billbug species (Coleoptera:Curculionidae: Sphenophorus parvulus Gyllenhal, S. venatus Chitt., S. inaequalis Say, and S. minimus Hart) found on New Jersey turfgrasses. A collection of 4803 adults from pure stands of various turfgrasses revealed all four billbugs on Kentucky bluegrass (Poa pratensis L.), tall fescue (Festuca arundinacea Schreb.), and perennial ryegrass (Lolium perenne L.), and S. parvulus, S. venatus, and S. minimus on Chewings fescue (F. rubra L. ssp. commutata Gaud.). Since the presence of larvae, pupae, or teneral adults more accurately indicates the host status of a grass species, immature billbugs were collected from plugs of the various grass species and reared to adults for identification. All four species were reared from immature billbugs found in Kentucky bluegrass turf; immatures of S. venatus, S. inaequalis, and S. minimus were found in tall fescue; S. venatus and S. minimus in perennial ryegrass; and S. inaequalis in strong creeping red fescue (F. rubra L. ssp. rubra). A laboratory experiment was also conducted in which billbug adults were confined in petri dishes with either Kentucky bluegrass, perennial ryegrass, tall fescue, or bermudagrass (Cynodon dactylon Pers.). Only minor differences were found between the four grasses in billbug survival, number of eggs laid, and amount of feeding. In general, bermudagrass was the least favored host and the other grasses were equally adequate hosts. The results of this study indicate a need for updating host-plant lists of these four billbug species.
K.L. Hensler, B.S. Baldwin, and J.M. Goatley Jr.
A bioorganic fiber seeding mat was compared to traditional seeding into a prepared soil to ascertain any advantages or disadvantages in turfgrass establishment between the planting methods. Bahiagrass (Paspalum notatum), bermudagrass (Cynodon dactylon), carpetgrass (Axonopus affinis), centipedegrass (Eremochloa ophiuroides), st. augustinegrass (Stenotaphrum secundatum), and zoysiagrass (Zoysia japonica) were seeded at recommended levels in May 1995 and July 1996. The seeding methods were evaluated under both irrigated and nonirrigated conditions. Plots were periodically rated for percent turf coverage; weed counts were taken about 4 weeks after study initiation. Percent coverage ratings for all grasses tended to be higher for direct-seeded plots under irrigated conditions in both years. Bermudagrass and bahiagrass established rapidly for both planting methods under either irrigated or nonirrigated conditions. Only carpetgrass and zoysiagrass tended to have greater coverage ratings in nonirrigated, mat-seeded plots in both years, although the percent plot coverage ratings never reached the minimum desired level of 80%. In both years, weed counts in mat-seeded plots were lower than in direct-seeded plots. A bioorganic fiber seeding mat is a viable method of establishing warm-season turfgrasses, with its biggest advantage being a reduction in weed population as compared to direct seeding into a prepared soil.