Southwest cupgrass was effectively controlled with preemergence herbicide impregnated fertilizer granules on non-overseed bermudagrass turf. Pendimethalin applied in two applications seven weeks apart (1.5 + 1.5 lb. AI/A) and Barricade applied once at 0.50 lb. AI/A provided 95-99% control. Team applied once at 3.0 lb. AI/A provided a maximum control of 93% by mid June. Team at the split rate of 1.5 + 1.5 lb. AI/A did not provide as high a level of control as the 3.0 lb. AI/A single application of Team.
 
 

A weed control test was conducted at the University of Arizona campus from March 2 to August 21, 1996, to evaluate Team, Pendimethalin, Dimension and Barricade herbicides as either single or split applications for pre-emergence control of Southwest cupgrass. This competitive summer annual weed normally germinates in the spring just as the non-overseeded bermudagrass shows signs of full green-up. It reproduces by seed and is best controlled via pre-emergence herbicide applications.

A large section of turf on the UA campus was selected for having a previous history of occurrence of Southwest cupgrass (Erichloa gracilis). Plot sizes varied from 5' X 15' to 5' X 5', depending on the areas of known infestation and estimated distribution within the turf. Ten replications of five treatments were applied on March 2 and (were applicable) again on April 21, 1996. All products were applied as granular impregnated fertilizer products with a 2.5 foot wide Gandy drop spreader. Treatments were applied at dawn and irrigated (3/8") by hand with a fan nozzle from a near-by quick coupler. Treatments were as follows: Team 0.87G at 3.0 lbs.; Team 0.87G at 1.5 + 1.5 lbs. (split application); Pendimethalin 0.86G at 1.5 + 1.5 lbs. (split application); Dimension 0.172G at 0.25 lbs.; Barricade 0.226 at 0.50 lbs. and untreated controls. All rates refer to active ingredient per acre. Each of the ten replications contained multiple checks either as similar sized plots or as adjacent alleys between each and all herbicide treated plots. Plots were evaluated for % plot green turf cover on seven different dates from March 27 to June 18, 1996. Plots were evaluated for the number of crabgrass plants per plot on seven different dates from April 19 to August 21, 1996. Plants counted on April 19, May 3 and May 16 were later identified as Dallisgrass (Paspalum dilatatum) and are not part of the analysis. Dallisgrass is as a weed and survives as short lateral coarse tillers from a sparse radial crown. Their initial appearance at green-up appeared like crabgrass but seed head formation allowed for a later and positive identification as Dallisgrass. Cupgrass was first positively identified on June 7 and is included in the analysis along with other valuations on June 18, July 31 and August 31. Check plots received no fertilizer. Plots were marked with turf paint for identification every ten days. Plots were mowed bi-weekly at 1.0 inches with a tri-plex reel mower. The turf received 1.0 inches of water from March 15 to April 31, and was irrigated with 1.5 inches of water per week from May 1 to the end of August..

Weed control was assessed as percent reduction compared to means of the control plots. The number of weeds within plots was normalized to obtain a uniform plot area for analysis. All data was analyzed using the analysis of variance technique using the ANOVA model on SAS for a randomized complete block design (RCBD) using ten replications. Tukey's honest least significant values (LSD values) were used for mean separation between herbicide treatments only if the herbicide treatment source of variation was significant at the P = 0.05 level as greater.

Turf Response

All herbicide products were impregnated on fertilizer carriers. On all seven evaluation dates, the treatments were significantly different from the checks for % green. These included the single one time "up front" treatments and the half rate repeat split application treatments of Pendimethalin and Team.

On March 27 (25 DAT/1), the Dimension and Team at the full 3.0 lb. rate had the highest % green turf ground cover (30%). This was followed by Barricade at 0.5 lb. and the half split rate of Team and Pendimethalin (around 20%). The check had 15% green ground cover area on average.

On April 10 (40 DAT/1), percent plot green values were little changed and treatments ranked similar to the March 27 evaluations.

By April 19 (48DAT/1), the overall green-up of the turf had almost doubled. There was a 10% difference between treated plots for % green ground cover (54% for Dimension to 42% for the split-half rate of Team). The check had 27% average green bermudagrass ground cover.

The second applicable split applications were made for Team and Pendimethalin (each at the 1.5 lb. rate) on April 21, 1996.

On May 3 (62 DAT/1:13 DAT/2) treated plots ranged between 52% to 61% plot green. All treated plots are statistically the same, but are different than the check.

By May 16 (75DAT/1:26 DAT/2), the split-half rate had better % plot green than the full "up front" rate (3.0 lb.) for Team. Pendimethalin and Team (at split rates) had 65% and 61% green plot cover, respectively. This was due to the second application of nitrogen from the half-rate (split) . Barricade (applied only once) was very close to that of the check (47% and 38%, respectively).

On June 7, treated plots ranged from 67% (Barricade) to 79% (Pendimethalin/split-rate) for green ground cover. The Team split-rate (1.5 + 1.5 lb.) had slightly greater green turf area than Team at the "up front" full rate application of 3.0 lb. The check plots were 55% green.

June 18 (108 DAT/1:60 DAT/2) was the last date for turf response measurements. The percent green turf for treated plots ranged from 78% to 84% and all herbicide treatments fell within the LSD value of 7% for statistical mean separation. Only the check was lower than all other (treated) plots at 69% green bermudagrass cover.

Cupgrass Control

As previously noted, cupgrass did not appear until the June 7 rating date. This was 97 days after the initial treatment and 48 days after the (applicable) second split application. Cupgrass weed control is reported for June 7, June 18, July 31 and August 21, 1996.

On June 7 (97 DAT/1:48 DAT/2) percent control between treatments was not significant. Control ranged from 78% (for Dimension at the one time application of 0.25 lb.) to 97% control for Pendimethalin (split application). Barricade was next at 95%, followed by Team. The Team at the "up front" initial rate of 3.0 lb. had about 10% better control than the split-rate (1.5 + 1.5 lb.) of Team (81% vs. 92%, respectively).

On June 18 (108 DAT/1:60 DAT/2), percent control ranged from 75% to 99% control. The one time full rate of Barricade (0.5 lb.) and split-rate of Pendimethalin had 99% control. Team at the initial single full rate application of 3.0 lbs. was superior to that of the split-rate of Team (1.5 + 1.5 lb.) at 93% vs. 75%, respectively.

On July 31, 1996 (150 DAT/1:102 DAT/2), weed control ranged from 76% to 99%. Pendimethalin and Barricade maintained 99% control. The full initial rate of Team (3.0 lb.) was slightly better than the initial and one time application of Dimension (0.25 lb.). The split application of Team (1.5 + 1.5 lb.) had the lowest control at 46%.

The last cupgrass counts were made on August 21, 1996. Mean control of cupgrass ranged from 80% to 99%. Pendimethalin and Barricade maintained 99% and 95% control respectively, which was statistically different in control than Dimension at 0.25 lbs. and Team at both the 1.5 + 1.5 lb. and 3.0 lb. rates. The increase in control by Team for the split application (80%) compared to the previous months weed counts may be possibly explained by the appearance of more robust plants, which could influence (bias) surface counts. It was noted that the checks had increasing numbers of plants per plot on all four evaluation dates.

1. The one time initial application of Dimension fertilizer combination provided greater amounts of percent plot green bermudagrass due to its high nitrogen value of 1.78 lbs. -N- acquired to achieve the 0.25 lb. AI/A herbicide rate. This was generally true from March to early May.

2. The split application treatments (Pendimethalin and Team) had greater percent green bermudagrass on plots from the second application, due simply to the late spring application of nitrogen.

3. Fertilizer impregnated Barricade (0.50 lb.) and Pendimethalin (1.5 + 1.5 lb.) had the highest control of cupgrass from June till the close of the test in late August.

4. Team at the one time 3.0 lb. rate achieved a maximum of 93% control by June 18.

5. Team at the 3.0 lb. rate provided better control of cupgrass than the split rate of Team (1.5 + 1.5) on four of five evaluation dates.

6. Emergence of Southwest cupgrass was considered late, although temperatures were normal.

7. Infestation levels of Southwest cupgrass progressed to high levels of infestation from June 7 to August 21 in the control (untreated) plots.

Appendix Table A. Pre-emergence herbicide treatments applied as fertilizer granules. University of Arizona, 1996.

Active Ingredient Fertilizer Analysis %
 

Product	Concentration	N	P	K	Number of applications	Lbs. nitrogen1 applied/per application	Lbs. active ingredient of herbicide per acre applied
Dimension	dithiopyr 0.172 (G)	28	4	8	1	1.78/1000 ft2	0.25
Barricade	prodiamine 0.22 (G)	19	4	6	1	1.00/1000 ft2	0.50
Prowl2	pendimethalin 0.86 (G)	28	3	4	2	0.79/1000 ft2	1.5 + 1.52
Team	balan/treflan 0.87 (G)	22	2	5	1	1.74/1000 ft2	3.0
Team3	balan/treflan 0.87 (G)	22	2	5	2	0.87/1000 ft2	1.5 + 1.53

¹Lbs. of nitrogen applied as herbicide impregnated fertilizer to achieve recommended herbicide application rate. Amounts listed are for a single application.

²Pendimethalin was applied twice (1.5 + 1.5 lb.)

³Team at the low rate was applied twice (1.5 + 1.5 lb.)

Table 1. Percent green bermudagrass turf¹ after applications² of herbicide applied as fertilizer granule treatments. University of Arizona, 1996.

Treatment	Lbs. AI/A Herbicide	MAR 27  (25 DAT/#1)  ---------------	APR 10  (40 DAT/#1)  ---------------	APR 19  (48 DAT/#1)  ---------------	MAY 3  (62 DAT/#1)  (13 DAT/#2)	MAY 16  (75 DAT/#1)  26 DAT/#2)	JUNE 7  (97 DAT/#1)  (48 DAT #2)	JUNE 183 (108 DAT/#1)  (59 DAT #2)
Dimension	0.25	31	32	54	61	53	71	81
Barricade	0.50	24	25	44	53	47	67	78
Pendimethalin	1.5 + 1.5	21	23	46	52	65	79	84
Team	3.0	30	26	44	56	50	71	80
Team	1.5 + 1.5	22	22	42	52	61	77	84
Check	-----	15	19	27	39	38	55	69
Date Mean4	-----	24	25	42	52	52	70	79
LSD Value5	-----	8	8	10	10	10	8	7

¹Percent turf green (0-100%). Values are mean of ten (10) replications.

²Initial treatments applied on March 2, 1996. All split applications for Pendimethalin and Team applied on April 21, 1996..

³Date of evaluation, followed by number of days after treatment (DAT) and application sequence 1 = initial, 2 = split.

⁴ Date Mean = Mean of all treatments and check on evaluation date.

⁵LSD Value = LSD mean separation statistic. Numerical differences between treatments means larger than the LSD value indicate true differences between treatments.

Table 2. Percent control¹ of Southwest cupgrass from select pre-emergence herbicides applied² on non-overseeded common bermudagrass turf. University of Arizona, 1996.

--------------------------------------% CONTROL--------------------------------------

Treatment	Lbs. AI/A Herbicide	June 7	June 18	July 31	August 21
Dimension	0.25	78	94	75	83
Barricade	0.50	95	99	96	95
Pendimethalin	1.5 + 1.5	97	99	99	99
Team	3.0	92	93	89	81
Team	1.5 + 1.5	81	75	46	80
Test Mean3	-----	89	92	81	87
LSD Value4	-----	NA	10	34	11
No weed plants  in check plots5	-----	26	33	138	208

¹Percent control = 1 - (treatment/control) X 100.

²Applications applied on April 21, 1996. Split applications (1.5 + 1.5) applied on April 21, 1996. No weeds appeared before the split application was applied on April 21, 1996.

³Test Mean = Mean of all treatments on each evaluation date.

⁴LSD Value = LSD mean separation statistic. Numerical differences between treatments means larger than the LSD value indicate true differences between treatments.

⁵Weed counts on check plots.

FN:CUPGRASS.96 DIR:Q396