Two rates of CONFRONT liquid herbicide (triclopyr plus clopyralid), one rate of a granular formulation with fertilizer (CONFRONT-ON- herbicide), and TRIMEC CLASSIC (industry standard) were applied to common bermudagrass turf (Cynodon dactylon) in order to asses summer time tolerance to CONFRONT herbicides. At 11 and 17 days after treatment (DAT), CONFRONT products tended to have slightly higher mean turf color scores than TRIMEC, although differences were subtle. CONFRONT-ON herbicide had decreased color scores at 7 DAT, perhaps due to the higher rate of active ingredient applied (0.84 lbs ai/a) or an unknown amount of fertilizer amount in the carrier. Turfgrass quality was significantly affected by herbicide treatments at 7 and 15 DAT, but not at 21 DAT. CONFRONT alone at 0.56 lb. ai/a produced some discoloration, leaf curling and cupping at 7 DAT. By 15 DAT, discoloration was no longer noticeable and turfgrass color and quality was equal or greater to that of the bermudagrass control plots.
 
 

Alternatives to non-phenoxy type herbicides are receiving greater interest among users for control of broadleaf weeds. The commercial product CONFRONT (mixture of triclopyr and clopyralid) was applied to common bermudagrass turf to assess the response of this turf to the CONFRONT herbicide. Triclopyr alone, especially in the ester formulation, often affects bermudagrass by producing off colored turf, slight twisting or spiraling of the leaves and reduced growth. This test was conducted to assess tolerance to the commercial mixture product CONFRONT (triclopyr plus clopyralid). TRIMEC CLASSIC was included as a industry standard.

The following treatments were applied to common bermudagrass turf in 5 x 8" plots on July 25, 1994. CONFRONT at 0.38 lb. ai/a, CONFRONT at 0.56 lb. ai/a, and CONFRONT/FERTILIZER at 175 lb. product/acre (0.84 lb. ai/a). Also included was TRIMEC CLASSIC (2,4-D, MCPA and dicamba) at 3 pints product/acre. This is equivalent to 1.25 lb. ai/a of TRIMEC.
The CONFRONT was applied using a Co₂ pressurized 3 boom nozzle at 20 inch spacing. The volume application rate was 115 gallons per acre at 30 psi using 8004 nozzles. CONFRONT/FERTILIZER was applied using a calibrated gandy sprayer. The granular product was watered in by hand after prior to spray treatments. The turf was common bermuda mowed twice weekly at 1.0 inches using a reel-type mower. The soil pH at the site was 7.2, with 2.0 % organic matter. Treatments were applied on July 27, 1994. Ambient air temperature was 99.7 F and the relative humidity was 24%. Soil type was a clay loam. Turf was evaluated on August 3, 11, and 17 for select response variables including color, quality, discoloration, tip burn, and leaf twisting where applicable. All treatments appeared six times in a randomized complete block design. Data was analyzed using ANOVA analysis on SAS and least significant difference values were calculated if the F ratio for herbicide treatments was significant at P = 0.05, or less.
 
 

August 3, 1994 (7 DAT):
Overall turfgrass color scores were not affected by herbicide applications. Mean color scores ranged from 5.2 to 6.3. The CONFRONT/FERTILIZER product had the lowest mean score of 5.2 (Table 1). Perhaps insufficient watering occurred following application or the carrier or total salt load was to extreme and cause mild damage.

Overall mean turf quality scores were affected by herbicide applications on August 3, 1994 (7 DAT). The 0.56 lb. ai/a of CONFRONT had the lowest quality score of 4.5, followed by the CONFRONT/FERTILIZER treatment (mean=5.0). The 0.38 lb. ai/a of CONFRONT was next at 5.8, followed by TRIMEC at 6.0. The control plots had a mean color score of 6.7 (Table 2). This demonstrated the slight effect herbicide application to common bermudagrass during mid-summer. Turfgrass discoloration scores were assigned to all plots using a 1-6 scale, where 1 = no discoloration and 6 = severe discoloration. Discoloration was subjectively scored using this scale relative to the degree of changes in turf color (light green). Only CONFRONT at the 0.56 lb. ai/a rate caused moderate discoloration (3.8 mean score), while other products were no different than that of the check plots (Table 3).

Leaf tip burn and twisting or cupping was also scored at 7 DAT, using the same relative scale as above for discoloration. The CONFRONT products showed increased tip burn over that of CONTROL (1.8) and TRIMEC (1.8). The 0.56 lb. ai/a rate of CONFRONT caused the most tip burning and twisting (mean = 3.3) at 7 DAT (Table 4).

August 11, 1994 (11 DAT):
Again, overall color scores were not significant due to treatments. Mean color scores ranged from 5.2 to 6.5. CONFRONT/FERTILIZER had the highest color score (6.5) while CONFRONT alone at 0.56 lb. ai/a had the lowest mean color (6.3) at 11 DAT (Table 1).

Mean quality scores ranked from 5.5 to 6.8, with check having the highest mean score. CONFRONT at 0.56 lb. ai/a and the CONFRONT/FERTILIZER had acceptable mean quality scores of 5.5. The lower CONFRONT rate of 0.38 lb. ai/a had a slightly better mean quality score of 6.0 (Table 2). Discoloration scores ranged from 1.2 to 2.1 by 15 DAT. Basically, all treatments showed some marginal discoloration over the check (Table 3).

August 17, 1994 (21 DAT):
At this time, color differences due to treatments exhibited the greatest effect. CONFRONT at 0.38 lb. ai/a had the highest mean color score (7.0) followed by the 0.56 lb. ai/a rate (6.8). All treatments had mean color scores of 6.0, or greater, with the check having the lowest mean color score of 5.7. Either nitrogen in the compounds (if any) or regrowth after slight damage may have caused increased color response among treated turfs at 21 DAT (Table 1).

Mean quality scores were not significantly affected by treatments at 21 DAT. An equal number of treatments had mean quality scores both above and or equal to or below the check mean of 5.8 (Table 2).

Table 1. Mean turfgrass color scores of common bermudagrass to select post-emergence products. University of Arizona, 1994.

Treatment¹ Rate² 03 August (7 DAT) 11 August (15 DAT) 17 August (21 DAT)

CONFRONT 0.38 lb. ai/a 6.3 6.0 7.0

CONFRONT 0.56 lb. ai/a 5.2 6.3 6.8

CONFRONT/FERTILIZER 175 lb. prod/a 6.0 6.5 6.0

TRIMEC CLASSIC 3 pints prod/a 5.7 5.8 6.3

CONTROL (none) 6.0 5.2 5.7

DATE MEAN⁴ 5.8 6.0 6.4

LSD VALUE⁵ -- -- 0.8

²Rate = in lbs. active ingredient/acre, or lbs. commercial product label, as listed.

³Mean of six replications. Color scores 1-9, 1 = straw color, 9 = dark green turf.

⁴Mean of all plots on each date.

⁵LSD values = least significant difference value. The difference between two treatment means must be larger than the LSD value for treatment differences to occur. "--" denotes not applicable as P values for treatment F test are greater than P = 0.05.

Table 2. Mean turfgrass quality scores of common bermudagrass to select post-emergence products. University of Arizona, 1994.

Treatment¹ Rate² 03 August (7 DAT) 11 August (15 DAT) 17 August (21 DAT)

CONFRONT 0.38 lb. ai/a 5.8 6.0 6.5

CONFRONT 0.56 lb. ai/a 4.5 5.5 6.2

CONFRONT/FERTILIZER 175 lb. prod/a 5.0 5.5 5.3

TRIMEC CLASSIC 3 pints prod/a 6.0 6.3 5.8

CONTROL (none) 6.7 6.8 5.8

DATE MEAN⁴ 5.6 6.0 5.9

LSD VALUE⁵ 0.9 1.0 --

²Rate = in lbs. active ingredient/acre, or lbs. commercial product label, as listed.

³Mean of six replications. Quality scores 1-9, 1 = dead turf, 9 = dark green turf.

⁴Mean of all plots on each date.

⁵LSD values = least significant difference value. The difference between two treatment means must be larger than the LSD value for treatment differences to occur. "--" denotes not applicable as P values for treatment F test are greater than P = 0.05.

Table 3. Mean turfgrass discoloration of common bermudagrass to select post-emergence herbicides. University of Arizona, 1994.

Treatment¹ Rate² 03 August (7 DAT) 11 August (15 DAT)

CONFRONT 0.38 lb. ai/a 2.7 1.3

CONFRONT 0.56 lb. ai/a 3.8 1.2

CONFRONT/FERTILIZER 175 lb. prod/a 2.8 1.7

TRIMEC CLASSIC 3 pints prod/a 2.2 1.8

CONTROL (none) 2.2 2.2

DATE MEAN⁴ 2.7 1.6

LSD VALUE⁵ 0.8 0.6

²Rate = in lbs. active ingredient/acre, or lbs. commercial product label, as listed.

³Mean of six replications. Discoloration mainly changes in leaf tip color 1-6, 1 = none, 6 = severe.

⁴Mean of all plots on each date.

⁵LSD values = least significant difference value. The difference between two treatment means must be larger than the LSD value for treatment differences to occur. "--" denotes not applicable as P values for treatment F test are greater than P = 0.05.

Table 4. Mean turfgrass damage (caused by tip burn and leaf twisting) of common bermudagrass to select post-emergence herbicides. University of Arizona, 1994.

Treatment¹ Rate² 03 August (7 DAT)

CONFRONT 0.38 lb. ai/a 2.2

CONFRONT 0.56 lb. ai/a 3.3

CONFRONT/FERTILIZER 175 lb. prod/a 3.0

TRIMEC CLASSIC 3 pints prod/a 1.8

CONTROL (none) 1.8

DATE MEAN⁴ 2.4

LSD VALUE⁵ 1.2

²Rate = in lbs. active ingredient/acre, or lbs. commercial product label, as listed.

³Mean of six replications. Damage scale 1-6, 1 = none, 6 = severe. Damage recorded as subjective evaluation of leaf tip burn and cupping/twisting.

⁴Mean of all plots on each date.

⁵LSD values = least significant difference value. The difference between two treatment means must be larger than the LSD value for treatment differences to occur. "--" denotes not applicable as P values for treatment F test are greater than P = 0.05.

Appendix Table A. Product analysis for 1994 post-emergence bermudagrass turf tolerance study. University of Arizona, 1994.

Treatment lbs. ai/a Acre Type N P K

CONFRONT 0.38 1 pint 3 SL 0 - 0 - 0

CONFRONT 0.56 7.5 pints 3 SL 0 - 0 - 0

CONFRONT/FERTILIZER¹ 0.84 175 lbs. .48G unknown?

TRIMEC CLASSIC 1.25 3 pints 3.3 EC 0 - 0 - 0

²TRIMEC CLASSIC comprised of 2.03 lb. 2,4-D, 1.08 MCPA and 0.21 lbs. dicamba (weight per gallon). Total ai/gallon is 3.32 EC.
 

FN: TRIWARM.RPT O/N/D 94 CLH