Management of annual bluegrass and bermudagrass in creeping bentgrass greens

Date

2012-08

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Abstract

Management of creeping bentgrass is relatively intense when maintained as a golf course putting green. The intense nature of the cultural practices required to maintain creeping bentgrass as a putting surface has a cumulative negative impact on this same environment. Aerification, verticutting, mowing, and topdressing open up the turfgrass canopy and cause significant wounding to creeping bentgrass plants. Voids in the canopy and reduced photosynthetic capability of desired turfgrass plants may shift the competitive edge to favor weed invasion. Experiments were conducted at the Plant and Soil Science greenhouse facility in Lubbock, TX in 2011 and 2012 on ‘Riviera’ and ‘Savannah’ common bermudagrass. Herbicide treatments were applied on December 1, 2011 and February 8, 2012 and consisted of metamifop at 200, 300, 400, and 500 g ai ha-1. A sequential application of each treatment was made on December 22, 2011 and February 29, 2012. An untreated check was included for comparison. The non-treated check pots exhibited 0% control and 0.59 to 0.83 g of biomass 3 weeks after initial treatment (WAIT), regardless of cultivar. Metamifop at 300 to 500 g ai ha-1 exhibited 96 to 100% bermudagrass control 3 WAIT, regardless of cultivar. Bermudagrass subjected to those same treatments exhibited 0.01 to 0.03 g of biomass 3 WAIT, regardless of cultivar. The 200 g ai ha-1 rate of metamifop exhibited 9% control of Savannah bermudagrass with 0.72 g of biomass collected, while Riviera was controlled 41% with 0.38 g of biomass collected. Sequential applications of metamifop at 300 to 500 g ai ha-1 completely controlled bermudagrass (100%) 6 WAIT, while a sequential application at 200 g ai ha-1 controlled bermudagrass 8 to 19% 6 WAIT, regardless of cultivar. Bermudagrass subjected to 200 g ai ha-1 exhibited 0.48 to 0.56 g of biomass 6 WAIT, regardless of cultivar. Experiments were conducted at the Plant and Soil Science greenhouse facility in Lubbock, TX in 2011 and 2012 on ‘Crystal Bluelinks’, ‘Penncross’, ‘Seaside II’, ‘Penn A-4’, ‘T-1’, and ‘L-93’ creeping bentgrass; and ‘SR 7200’ velvet bentgrass. Herbicide treatments were applied on December 1, 2011 and February 8, 2012 and consisted of metamifop at 200, 300, 400, and 500 g ai ha-1. A sequential application of each treatment was made on December 22, 2011 and February 29, 2012. An untreated check was included for comparison. Metamifop at 200 to 300 g ai ha-1 exhibited 0 to 7% bentgrass phytotoxicity 3 WAIT, regardless of cultivar. Metamifop at 400 to 500 g ai ha-1 exhibited 12 to 18% phytotoxicity on L-93 and Penn A-4, while phytotoxicity on all other cultivars was ≤ 8% 3 WAIT. The phytotoxicity observed on L-93 and Penn A-4 in response to metamifop at 400 to 500 g ai ha-1 coincided with large reductions in biomass (72 to 91%) compared to the untreated checks 3 WAIT. All bentgrass cultivars exhibited ≤ 10% phytotoxicity in response to metamifop at 200 g ai ha-1 6 WAIT. Bentgrass cultivars responded differently to applications of metamifop at 300 g ai ha-1 6 WAIT. Phytotoxicity was only 10% for Crystal Bluelinks, 18% for Seaside II, 18% for SR 7200, and 26% for T-1. Phytotoxicity was 47 to 76% for the remaining cultivars 6 WAIT. Seaside II, SR 7200, T-1, and Crystal Bluelinks exhibited 24 to 36% phytotoxicity in response to metamifop at 400 g ai ha-1 6 WAIT, while all other cultivars exhibited 70 to 86% phytotoxicity. Seaside II, SR 7200, and Crystal Bluelinks exhibited 48 to 51% phytotoxicity in response to metamifop at 500 g ai ha-1 6 WAIT, while all other cultivars exhibited 69 to 88% phytotoxicity. High levels of phytotoxicity 6 WAIT coincided with large amounts of biomass reduction when compared to the untreated check. Three field experiments were conducted on creeping bentgrass greens at separate locations between the fall of 2011 and the spring of 2012 in Lubbock, TX. Herbicide treatments were initiated on October 10, 2011, November 10, 2011, or December 10, 2011 and consisted of single or sequential applications of methiozolin at 0.5 or 1.0 kg ai ha-1. Sequential applications were made in one-month increments. Paclobutrazol at 0.28 kg ai ha-1 applied on October 10, 2011 with a sequential application on November 10, 2011 was evaluated as an industry standard. An untreated check was included for comparison. Minimal to no creeping bentgrass phytotoxicity (< 2.5%) was observed 28 DAIT in response to methiozolin, regardless of application rate or timing. Paclobutrazol treatments in our research exhibited 30% creeping bentgrass phytotoxicity 28 DAIT. However, phytotoxicity was reduced below acceptable levels (< 10%) by the following spring. Differences in annual bluegrass control were observed between locations. Methiozolin applications at the Rawls Golf Course exhibited 57 to 86% annual bluegrass control, regardless of application rate or timing. Control increased as applications were made later in the fall. Single applications of methiozolin applied in October exhibited 57 to 63% control, while applications made in December exhibited 65 to 73% control, regardless of rate. Annual bluegrass control in response to methiozolin at the Reese Golf Course ranged from 54 to 100%, regardless of application rate or timing. Control increased as applications were made later in the fall. Single applications of methiozolin applied in October exhibited 54 to 78% control, while applications made in November exhibited 78 to 88% control, regardless of rate. However, control was only 74% in response to single applications of methiozolin made in December, regardless of rate. The number of sequential applications of methiozolin significantly affected annual bluegrass control . Control was 63, 74, and 82% at the Rawls Golf Course in response to methiozolin applied 1, 2, and 3 times, respectively, regardless of application rate or application timing. Control was 75, 90 and 95% at the Reese Golf Course in response to methiozolin applied 1, 2, and 3 times, respectively, regardless of application rate or timing.

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Keywords

Annual bluegrass, Agrostis, Bermuda grass

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