|
December 16, 2007
Seashore Paspalum Traffic Tolerance – Grow In Update
The grow-in of research plots at the National Memorial Cemetery of the Pacific is in full swing. While recent wet weather has helped the establishment of both sod and stolons, plots seeded to ‘Sea Spray’ seashore paspalum have not fared as well. Heavy rains caused washout shortly after seeding. Wet weather and bare soil have combined to create a favorable environment for the development of winter weeds. Hopefully, rains will subside allowing these areas to be sprayed with herbicides and re-seeded. |
 Seashore Paspalum – Bermudagrass Competition Study Underway
Seashore paspalum contamination of hybrid bermudagrass greens is common throughout Hawaii. In some instances, greens that were once 100% hybrid bermudagrass are now more than 70% seashore paspalum (Figure 1). Preliminary studies are underway at Ewa Villages Golf Course (Ewa, HI) evaluating chemical programs to reduce hybrid bermudagrass competition with seashore paspalum. Effective programs may have the ability to slowly transition these greens to 100% seashore paspalum over time.
Applications of plant growth regulators flurprimidol (Cutless) and paclobutrazol (Trimmit) will be evaluated alone and in combination with herbicides such as ethofumesate (Prograss), siduron (Tupersan), triclopyr (Garlon/Turflon), and granular salt. All materials will be applied at both full and partial label rate to plots receiving both high and low levels of nitrogen fertility. Turfgras color, foliar injury, and chlorophyll content will be measured 1 and 4 weeks after each application. Changes in the percentage of hybrid bermudagrass per plot will be determined when the study is completed in April.
Plot images will be posted throughout the study. Thanks go out to Ms. Heide Madrigal, CGCS for collaborating in this research effort.
Alternative Weed Control in Seashore Paspalum
 Initial studies at Ko’olau G.C. and Coral Creek G.C. concluded on 4 December 07. Although soil sodium data has not yet been analyzed, we can report that applications of salt provided effective control of both hilograss (Paspalum conjugatum) and goosegrass (Eleusine indica). Applications of fine granular materials (83% 0.50-0.25 mm) provided greater control than coarser products.  While spray applications exhibited efficacy, this strategy proved to be impractical. In order to apply an effective dose of material, spray volumes needed to be far greater than 40 gallons per acre.
Two applications of fine granular salt, at a rate of 10 lbs per 1000 ft2, provided nearly 100% control of hilograss for 8 weeks after initial treatment (Figure 2). Granular applications at this rate did not effectively control goosegrass. No treatments caused turfgrass color to become unacceptable during the 8 week study (Figure 3). Salt applications at higher rates provided efficacy against both hilograss and goosegrass soon after treatment, but re-growth was observed (Figure 4).
 The reduced efficacy of granular applications on goosegrass may be attributed to the presence of moisture on the leafblade. Applications at Ko’olau (targeting hilograss) were made when dew was still present on the leaf blade, while applications at Coral Creek (targeting goosegrass) were made to dry foliage. Delivering the same amount of material as a solution at Coral Creek provided nearly 100% control of goosegrass 8 weeks after initial treatment.
Applications of MSMA and metribuzin (Sencor) failed to control hilograss but provided nearly 100% control of goosegrass. Two applications of foramsulfuron (Revolver) at the high label rate effectively controlled goosegrass as well. All herbicide applications (MSMA, Sencor, Revolver) reduced turfgrass color below acceptable levels (Figure 5).
We plan to initiate more studies evaluating the use of high salt index materials as analternative to herbicide on seashore paspalum after the first of the year. The efficacy of potassium and calcium chloride will be compared to sodium chloride at the 10 lb rate discussed herein. Additionally, we plan to evaluate the efficacy of lower application rates for control of hilograss and goosegrass. Stay tuned!
 NOTE: UNTIL SOIL AND METEROLOGICAL DATA ARE FULLY ANALZYED, SALT APPLICATIONS TO CONTROL THESE WEEDSARE NOT RECOMMENDED. WHILE EFFICACY WAS REPORTED, THE EFFECT OF THESE TREATMENTS ON SOIL QUALITY REMAINS UNKOWN. APPLICATIONS AT THESE RATES MAY HAVE CAUSED LONG TERM DAMAGE TO SOIL QUALITY. DATA NEED TO BE FULLY ANALYZED BEFORE CONCLUSIONS CAN BE MADE.
|
