Tese treatments included: dazomet alone at 262 lbs ai/acre; dazomet applied twice (5 days apart) at 262 lbs ai/acre; dazomet alone at 525 lbs ai/acre; 1 application of glyphosate + fluazifop alone; 2 and 3 applications of glyphosate + fluazifop alone (approximately 30 days apart); glyphosate + fluazifop followed by dazomet at 262 lbs ai/acre 5 days apart; or a single application of dazomet at 525 lbs ai/acre.
All plots were core-aerified 3 days before application and irrigated daily from 3 to 1 days prior to dazomet application to ensure sufficient soil moisture. One day prior to application, all plots were scalped (0.5 inches/1.25 cm) with a mower to conform with labeled recommendations. On the day of initial dazomet application, select plots were tilled using a tractor-mounted roto-tiller in two directions to a depth of 6 inches (15 cm). Dazomet applications were then applied using a drop-spreader after which various tillage, rolling, irrigation, and tarping treatments were performed at the prescribed timing from Table 1.
Table 1. Dazomet treatment descriptions and incorporation methods for field studies conducted in North Carolina and Texas.pp
Dazomet
(Herbicide; pounds ai/acre) (DAZy; 262)
(FLUx + GLY) fb (DAZ; 262) (DAZ; 262) fb (DAZ; 262)
(FLU + GLY) fb (DAZ; 262) fb (DAZ; 262) (DAZ; 525) (DAZ; 525)
(FLU + GLY) fb (DAZ; 525) (FLU + GLY) fb (DAZ; 525)
(FLU + GLY) fb (DAZ; 525) (FLU + GLY) (FLU + GLY)
(FLU + GLY) fb (FLU + GLY) (FLU + GLY) fb (FLU + GLY) fb (FLU + GLY)
Timing (days)z 7
0 fb 7 7 fb 12
0 fb 7 fb 12 7 7
0 fb 7 0 fb 7
0 fb 7 0 0
0 fb 30 or 32 (NC or TX) 0 fb 30-32 fb 56 or 49 (NC or TX)
Nontreated --- Nontreated ---
z Day 0 applications initiated May 25, 2015 in Raleigh, NC and June 15, 2015 in College Station, TX. y Abbreviations: DAZ, dazomet; FLU, fluazifop; GLY, glyphosate; fb, followed by x Fluazifop (0.4 pounds/acre) and glyphosate (3 pounds/acre).
All plots were then evaluated visually for bermudagrass cover estimated on a 0 percent (no bermudagrass cover) to 100 percent (complete bermudagrass cover) scale at 8, 15, and 46 weeks after initial treatment (WAIT) in NC and at 5, 10, 16, and 42 WAIT in Texas. Bermudagrass cover was also estimated using a line-intersect method at both locations where a grid was placed above each plot and intersections with bermudagrass beneath them were divided by the total number of intersections.
In North Carolina, dazomet-alone resulted in unacceptable bermudagrass control (> 10 percent cover) from 8 to 46 WAIT (45 to 85 percent cover; Figure 1). Fluazifop + glyphosate applied one week prior to dazomet application(s) reduced bermudagrass cover to < 10 percent from 8 to 46 WAIT. Within these treatments, a single irrigation-incorporated dazomet application at 262 pounds/acre resulted in 1 to 6 percent bermudagrass cover, which was comparable to the 525 pounds/acre rate (0 to
TPI Turf News March/April 2019 51
1 percent) and a sequential application of 262 pounds/ acre (0 to 3 percent). Tis suggests fluazifop + glyphosate application prior to dazomet can reduce total dazomet requirements for acceptable bermudagrass control. Additionally, the current maximum single application allowance for dazomet soil-incorporation by water is 262 pounds/acre, which these results support its utility for bermudagrass eradication.
incorporation Irrigate Irrigate Irrigate Irrigate Irrigate
Till fb roll Irrigate
Till fb roll
Till fb roll fb tarp ---
Till --- ---
Till ---
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