| Abstract/Contents: | "Annual bluegrass (Poa annua) is a problem in bentgrass (Agrostis palustris) fairways. It reduces aesthetic quality and when seedheads are present can affect play of the golf course. Annual bluegrass and creeping bentgrass are cool season turfgrass species, therefore selective control is difficult. Also, once annul bluegrass has perennialized, few control measures have proven acceptable for golf course use. Research objectives were to screen herbicides, labeled turfgrass fungicides, and surfactants in different application strategies for bluegrass control and bentgrass tolerance. In the fall 1996, screenings were conducted on a bentgrass fairway. Plots were maintained by the staff at Wade Hampton Golf Club in Cashiers, North Carolina. Plots were 1.5 m x 3.0 m in a randomized complete block design with 4 replications. Using a CO₂ backpack sprayer, treatments were applied monthly beginning in September, and concluding in December. Treatments included ethofumesate (0.74 lbs ai/A), ethofumesate (0.74 lbs ai/A) + Urea(6.44 lbs N/A), glyphosate (0.063 lbs ai/A), pelargonic acid (0.066 lbs ae/A), glyphosate (0.03 lbs ai/A) + pelargonic acid (0.033 lbs ae/A), glufosinate (0.016 lbs ai/A), and glufosinate (0.031 lbs ai/A). For all treatments, the September and October applications were applied at 20 gpa. For November and December applications, treatments containing glyphosate, pelargonic acid, and glufosinate were applied at 80 gpa in an attempt to reduce turfgrass injury. In 1997, treatments were applied to the same fairway on different plots in similar manner as the previous year. However, treatment application timings varied. Glyphosate (0.063 lbs ai/A), diquat (0.031 lbs ai/A) + Optima (0.5% v/v), ethofumesate (1 lb ai/A), and glyphosate (0.063 lbs ai/A) + diquat (0.031 lbs ai/A) were applied in October, November, and December. Clethodim (0.048 lbs ai/A) + Optima (0.5% v/v), clethodim (0.095 lbs ai/A) + Optima (0.5% v/v), and clethodim (0.048 lbs ai/A) + diquat (0.031 lbs ai/A) + Optima (0.5% v/v) were applied only in October. While fluazifop (0.047 lbs ai/A) + Optima (0.5% v/v) and fluazifop (0.047 lbs ai/A) + diquat (0.031 lbs ai/A) + Optima (0.5% v/v) were applied in October and December. The 1998 evaluations included three seperate studies on the same fairway as the previous 2 years. Study 1 was similar to 1996 and 1997 evaluations. Treatments included glyphosate (0.125 lbs. ai/A), diquat (0.031 lbs ai/A) + Primer (1% v/v), glyphosate (0.125 lbs ai/A) + diquat (0.031 lbs ai/A), fenoxaprop (0.38 lbs ai/A) + triclopyr (1.0 lb ai/A), bentazon (1.5 lbs ai/A), bentazon (1.5 lbs ai/A) + diquat (0.031 lbs ai/A), and Primer (1% v/v). All treatments were applied at 80 gpa in September, October, and November, however the October reapplication for fenoxaprop + triclopyr was omitted due to excessive bentgrass injury. Study 2 treatments were labeled turfgrass fungicides and a plant growth regulator. Treatments included fenarimol (1.021 lbs ai/A), myclobutanil (0.98 lbs ai/A), cyproconazol (0.545 lbs ai/A), paclobutrazol (0.25 lbs ai/A) alone, and combinations of each treatment with paclobutrazol. All treatments were applied in September, October, and November at 20 gpa. Treatments in study 3 were from the sulfonylurea family and included primsulfuron, rimsulfuron, tiasulfuron, and chlorimuron. All treatments were applied at two rates (0.016 lbs ai/A and 0.032 lbs ai/A) in September and November at 20 gpa. For all three years, visual annual bluegrass control ratings were made on a 0% to 100% scale, 0%=no control, 70%= minimal acceptable control, and 100%=no annual bluegrass. Visual bentgrass injury was rated on a 0% to 100% scale, 0%= no injury, 30%= maximum allowable injury, and 100%= complete death. No treatment provided acceptable ($70%)annual bluegrass control at any time. The greatest control (.50 to 70%) was observed with glyphosate in 1996 and 1998 and with rimsulfuron in 1998. Bentgrass injury was observed for various treatments and was not consistent from year to year. In 1996 and 1998, glyphosate treated plots had severe bentgrass injury ($ 50%). Yet in 1997, bentgrass injury resulting from glyphosate did not exceed 10%, however rates and delivery volume varied between years. Other treatments that severely injured bentgrass included combinations of clethodim ($ 70%), combinations of fluazifop ($ 70%), fenoxaprop + triclopyr($ 70%), combinations of a fungicide and paclobutrazol ($ 35%), and both rates of rimsulfuron ($ 35%)." |
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