Pre-emergence herbicides including Dimension (dithiopyr) Stomp (pendimethalin) Ronstar (oxadiazon), Barricade (prodiamine), Surflan (oryzalin), Gallery (isoxaben), Team (treflan plus benefin) were applied in various formulations and rates to assess weed control of southwestern cupgrass (Erichloaacuminata). Dimension clay granules at 0.38 and 0.50 lb ai/A rates provided season long control with one application. Barricade also produced equal control as Dimension. Ronstar at the 3.0 lb ai/A rate also had 96-100% control throughout the season along with Best fertilizer (Team herbicide with fertilizer blended). Dimension granules were slightly better than the liquid (EC formulation). Repeat applications of select treatments at six weeks were erroneously omitted. Turfgrass density and percent bermudagrass plot cover in mid-May were effected by herbicide treatments.

Turfs in southern Arizona are subject to infestation with summer annual weeds, which include crabgrass (Digitaria spp.) and southwestern cupgrass (Eriochloa acuminata). These species are quite competitive in turfs of even modest density, and reproduce from the germination of abundant seeds produced by late summer. Pre-emergence control can be an effective (and preferred) means of controlling these weeds. Such pre-emergence control warrants application of herbicides in late February or early March in the low desert valleys of Phoenix and Tucson. A replicated field trial was conducted at Mesa Community College to assess the weed control properties of selected herbicides, and herbicide/fertilizer combinations.

The turf site included a large area of known infestations of grassy weeds, which was exclusively that of southwestern cupgrass. The turf during the winter was that of annual ryegrass (Lolium multiflorum), which was mowed at 2.5 inches with a riding rotary mower. The turf site was irrigated to prevent visual stress.

Applications of pre-emergence herbicides were made on March 9, 1993. Post emergence treatments (where applicable) were made on July 7, 1993. A scheduled repeat application for five herbicide treatments (split application) was erroneously omitted. Liquid applications were made using a two nozzle boom at 20 inch spacing. Plot size was 40" x 84". Carrier volume was 85.5 gal/A. Nozzle size was 8004 and tank pressure was 30 psi. Granular applications were made using a Gandy 36" width drop spreader, calibrated for each treatment. Treatments were incorporated within 2 hours after application with 1/4-3/8 inches of supplemental irrigation.

A total of 33 treatments were applied (Appendix Table -A-). Turf plots were evaluated for cupgrass control based on the percent of the control plots. Where applicable, either the mean of all control plots or specific weed infestation levels (control levels on a per-replication basis) was used as the value for which weed control was assessed. This decision was based on potential differences in weed densities among control plots, and if the F value probability statistic for the multiple check plots was greater than 1.0.

Response variables included percent weed control, turfgrass quality, density, texture, percent plot straw, percent plot ryegrass and bermudagrass (when and where applicable).

Density:
Density scores were assigned on April 8, May 13, June 9, July 7 and August 16. The density scores for April 18 and June 9 were significant at the P = 0.19 and P = 0.01 levels, respectively. These mean values are reported in Table 1.

Percent Plot Straw:
Visual observations were made on the percent plot straw (% turf which was brown) on May 13, June 9, and July 7. The amounts recorded were not related to herbicide treatments, as F ratios were low, and P values ranged from P = 0.35, to P = 0.94. The percent plot straw was most likely the transition of the annual ryegrass, which can often fade quickly in the heat of late spring under high temperatures. Potential interactions with differences in irrigation and low fertility may also cause random expression of this variable (data not shown).

Percent Plot Green Ryegrass:
On May 13 and June 9, the percentage of the plot which had green living annual ryegrass was scored (0-100% of the entire plot). Treatment effects were not statistically significant, however, a wide range of responses were noted on the May 13 evaluation date. Mean treatment responses are given in Table 2. Means between treatments ranged from 15 to 57%. Remaining plot cover was also covered with declining annual ryegrass and common bermudagrass.

Percent Bermudagrass:
Percent plot bermudagrass (0-100%) was recorded on May 13, June 9, and July 7, 1993. The effect of herbicide treatments was statistically significant on May 13 (P = 0.01). Results are given in Table 3. Percent bermudagrass ranged from 12%, to 52%. By June 9, 1993, percent bermuda ranged from 48 to 95% (data not shown) and from 50 to 96% on July 7 (data not shown). On June 9 and July 7, the percent bermudagrass was not affected by herbicide treatments.

Weed Control:
The efficiency of the herbicide treatments was determined on June 9, July 7, August 16 and September 27. Southwestern cupgrass was not present on the May 13 evaluation date. The herbicide treatment effect was highly significant on all dates, except on July 7 (p = 0.18).

The percent weed control is provided in Table 4. On June 9, (92 DAT) 100% weed control was realized by the following treatments:

1) Prodiamine 0.75 lbs ai/A

2) Best Fertilizer/Team 3.0 lbs ai/A

3) Ronstar 3.0 lbs ai/A

4) Dimension -G- 0.38 lbs ai/A

5) Dimension -G- 0.50 lbs ai/A

6) Pendimethalin/Fert 3.0 lbs ai/A

7) Pendimethalin Exp -G- 4.9 lbs ai/A

8) Stomp 4.9 lbs ai/A

There were eleven other treatments which exhibited 95-99% mean weed control levels. Best fertilizer contained the herbicide 'TEAM' (Benefin+Trifluralin) as a commercial product.

Treatments which had 85% or less control at this time included BEST-FERTILIZER product at 1.5 lbs ai/A, GALLERY/SURFLAN/FERTILIZER (233 lbs product/A), SURFLAN AS. at 2.0 lbs ai/A, and Dimension liquid at 0.125 lbs ai/A (Table 4).

On July 8 (121 DAT), weed control ranged from 13% to 100%. The Dimension granule (-G-) products at 0.5 and 0.38 lbs ai/A had 100% control. Dimension liquid at 0.50 lbs ai/A had 98% control. Eight products had 95-99% control. These included pendimethalin fertilizer (3.0 lb ai/A), Prodiamine at 1.0 lb ai/A, GALLERY/TEAM-Fertilizer (375 lbs product/A) and Ronstar at 3.0 lbs ai/A. SURFLAN AS. at the rates tested here had 67% or less weed control (Table 4).

On August 16 (160 DAT), weed control mean treatment values ranged from 0 to 100% (full control). Dimension clay granules (-G-) at both the 0.38 and 0.50 lb ai/A rates had 100% control, along with pendimethalin-fertilizer (3.0 lb ai/A), Prodiamine (1.0 lb ai/A) and GALLERY/TEAM-Fertilizer (375 lb prod/A). Seven other treatments had 95-99% control, as well (Table 4).

The post emergence applications of Quinclorac/MSMA, and Illoxan/Surflan, had 71% and 0% control, respectively. All together, eleven treatments had weed control levels of less than 90% (Table 4).

The last evaluation for weed control was on September 22 (197 DAT). Dimension clay granules (-G-) and Pendimethalin + fertilizer at the high rate of 3.0 lbs ai/A had 100% control. Seven other treatments had 96-99% control of cupgrass. These included Dimension (-G-) at 0.38 lbs ai/A, Prodiamine at both the 0.75 lb ai/A and 1.0 lb ai/A rates, Dimension -G- at 0.25 lb ai/A, Gallery + Team fertilizer at 375 lbs product/A, Best fertilizer at 3.0 lbs ai/A, and Ronstar at 3.0 lbs ai/A.

FN: MCCWEEDS.93 O/N/D CLH

Table 1. Mean¹ turfgrass density values for turf treated with selected pre-emergence herbicides. University of Arizona, 1993. Pre-emergence applied on March 7, 1993.
April 8, 1993 June 9, 1993

Density Density

TREATMENT² MEAN TREATMENT²MEAN

SURFLAN AS 1.5 lb/A 5.0 GALLERY/TEAM/FRT 375 lb P/A 6.0

SURFLAN AS 2.0 lb/A 5.0 DIMENSION 0.50 lb/A 5.7

GALLERY/TEAM/FRT 375 lb P/A 4.8 SURFLAN AS 2.0 lb/A 5.7

DIMENSION 0.50 lb/A 4.8 DIMENSION 0.38 lb/A 5.7

BEST-FRT 1.5 lb/A 4.6 SURFLAN+ILLOXAN 1+0.5 lb/A 5.7

RONSTAR 3.0 lb/A 4.6 QUINCLORAC+MSMA .5+2 lb/A 5.7

DIMENSION CLAY GRAN. 0.50 lb/A 4.4 SURFLAN/FERT 2.0 lb/A 5.3

QUINCLORAC+MSMA .5+2 lb/A 4.3 RONSTAR 3.0 lb/A 5.0

GALLERY/SURFLAN/FRT 233 lb/A 4.3 SURFLAN AS 1.5 lb/A 5.0

PRODIAMINE 0.5 lb/A 4.2 BEST-FRT 3.0 lb/A 5.0

PENDIMETHALIN/FRT 1.5 lb/A 4.1 DIMENSION CLAY GRAN. 0.25 lb/A 5.0

BEST-FRT 3.0 lb/A 4.1 XL 1.5 lb/A 4.7

DIMENSION CLAY GRAN. 0.38 lb/A 4.1 GALLERY/SURFLAN/FRT 233 lb P/A 4.7

PRODIAMINE 1.0 lb/A 4.1 XL 3.0 lb/A 4.7

CHECK 4.1 PENDIMETHALIN/FRT 3.0 lb/A 4.7

PENDIMETHALIN/FRT 3.0 lb/A 3.9 CHECK 4.6

PENDIMETHALIN EXP GR 2.45 lb/A 3.9 STOMP 4.90 lb/A 4.5

XL 1.5 lb/A 3.9 DIMENSION 0.125 lb/A 4.3

PRODIAMINE 0.75 lb/A 3.9 STOMP 2.45 lb/A 4.3

STOMP 4.90 lb/A 3.7 PENDIMETHALIN/FRT 1.5 lb/A 4.0

SURFLAN+ILLOXAN 1+0.5 lb/A 3.7 GALLERY/TEAM/FRT 250 lb P/A 4.0

STOMP 2.45 lb/A 3.7 DIMENSION CLAY GRAN. 0.38 lb/A 4.0

DIMENSION CLAY GRAN. 0.25 lb/A 3.7 PRODIAMINE 0.5 lb/A 4.0

SURFLAN/FERT 2.0 lb/A 3.7 DIMENSION CLAY GRAN. 0.50 lb/A 4.0

DIMENSION 0.38 lb/A 3.5 PENDIMETHALIN EXP GR 2.45 lb/A 4.0

DIMENSION 0.125 lb/A 3.5 PRODIAMINE 1.0 lb/A 3.7

PENDIMETHALIN EXP GR 4.90 lb/A 3.5 PRODIAMINE 0.75 lb/A 3.7

GALLERY/TEAM/FRT 250 lb P/A 3.3 PENDIMETHALIN EXP GR 4.90 lb/A 3.7

XL 3.0 lb/A 3.3 BEST-FRT 1.5 lb/A 3.0

LSD Value³ --- LSD Value³ 1.4

¹Means are values of 3 replications. Value scores 1-6, 6 = most dense.

²Quinclorac/MSMA and Surflan/Illoxan were applied post emergence, July 7, 1993. All others were applied pre-emergent on March 9, 1993. Application rates are lbs ai/A, unless otherwise noted lb P/A = lbs product/acre.

³LSD Value = Least significant difference statistic. Difference between two treatment means must be greater than the LSD value for statistical difference to occur between treatment means. Used only if herbicide effect is P=0.05 or less.

Table 2. Percent plot Living Green¹ perennial ryegrass after application of select pre-emergence herbicides. University of Arizona, 1993.

TREATMENT³ MEAN
 

QUINCLORAC+MSMA (POST) 0.5+2.0 lb/A 57

RONSTAR 3.0 lb/A 52

DIMENSION 0.125 lb/A 48

STOMP 4.90 lb/A 48

BEST-FRT 3.0 lb/A 45

DITHIOPYR 0.50 lb/A 43

DIMENSION 0.38 lb/A 42

PRODIAMINE 0.5 lb/A 42

PRODIAMINE 0.75 lb/A 40

UN-TREATED CHECK 38

PENDIMETHALIN EXP GRANULE 2.45 lb/A 38

GALLERY/SURFLAN/FRT 233 lbs. P/A 37

PRODIAMINE 1.0 lb/A 37

STOMP 2.45 lb/A 35

DIMENSION CLAY GRANULE 0.38 lb/A 35

XL 3.0 lb/A 33

DIMENSION CLAY GRANULE 0.25 lb/A 33

DIMENSION CLAY GRANULE 0.50 lb/A 32

BEST-FRT 1.5 lb/A 30

SURFLAN+ILLOXAN (POST) 1+0.5 lb/A 30

PENDIMETHALIN/FRT 1.5 lb/A 28

PENDIMETHALIN EXP GRANULE 4.90 lb/A 28

SURFLAN AS 1.5 lb/A 28

GALLERY/TEAM/FRT 250 lbs. P/A 27

XL 1.5 lb/A 25

SURFLAN AS 2.0 lb/A 22

GALLERY/TEAM/FRT 375 lb P/A 17

SURFLAN/FERT 2.0 lb/A 15

PENDIMETHALIN/FRT 3.0 lb/A 15

LSD Value² --

²LSD Value = Least significant difference statistic. Difference between two treatment means must be greater than the LSD value for statistical difference to occur between treatment means. Used only if herbicide effect is P=0.05 or less.

³Quinclorac/MSMA and Surflan/Illoxan were applied post emergence, July 7, 1993. All others were applied pre-emergence on March 9, 1993. Application rates are in lbs ai/A, except where noted as lbs product/acre (P/A).

Table 3. Mean percent bermudagrass plot cover after an application of select post emergence herbicides. University of Arizona, 1993.

TREATMENT² MEAN¹

GALLERY/TEAM/FRT 375 lb P/A 52

SURFLAN/FERT 2.0 lb/A 47

SURFLAN AS 2.0 lb/A 42

PENDIMETHALIN/FRT 3.0 lb/A 38

SURFLAN+ILLOXAN 1+0.5 lb/A 37

SURFLAN AS 1.5 lb/A 35

XL 1.5 lb/A 35

PENDIMETHALIN/FRT 1.5 lb/A 30

DIMENSION CLAY GRANULE 0.25 lb/A 28

QUINCLORAC+MSMA 0.5+2.0 lb/A 28

GALLERY/TEAM/FRT 250 lb P/A 27

CHECK 27

GALLERY/SURFLAN/FRT 233 lb P/A 25

DITHIOPYR 0.38 lb/A 25

PRODIAMINE 0.5 lb/A 23

DITHIOPYR 0.50 lb/A 23

STOMP 2.45 lb/A 23

BEST-FRT 3.0 lb/A 23

BEST-FRT 1.5 lb/A 20

XL 3.0 lb/A 20

STOMP 4.90 lb/A 20

PRODIAMINE 1.0 lb/A 18

DIMENSION CLAY GRANULE 0.38 lb/A 18

DITHIOPYR 0.125 lb/A 15

RONSTAR 3.0 lb/A 15

PENDIMETHALIN EXP GRANULE 4.90 lb/A 15

PRODIAMINE 0.75 lb/A 15

DIMENSION CLAY GRANULE 0.50 lb/A 13

PENDIMETHALIN EXP GRANULE 2.45 lb/A 12

LSD Value³ 21

²Quinclorac/MSMA and Surflan/Illoxan were applied post emergence, July 7, 1993. All others were applied pre-emergence March 9, 1993.

³LSD Value = Least significant difference statistic. Difference between two treatment means must be greater than the LSD value for statistical difference to occur between treatment means. Used only if herbicide effect is P=0.05 or less.

Table 4. Pre-emergent control of Southwestern cupgrass on four dates in 1993 expressed as [1-(treatment/control)] x 100.

University of Arizona.
 

JUNE 9 (92 DAT)

JULY 8 (121 DAT)

AUGUST 16 (160 DAT)

SEPTEMBER 22 (197 DAT)

 

TREATMENT	%	TREATMENT	%	TREATMENT	%	TREATMENT	%
DIMENSION -G-  0.50 lb/A	100	DIMENSION -G-  0.50 lb/A	100	DIMENSION -G-  0.50 lb/A	100	DIMENSION -G-  0.50 lb/A	100
DIMENSION -G-  0.38 lb/A	100	DIMENSION -G-  0.38 lb/A	100	DIMENSION -G-  0.38 lb/A	100	PENDIMETHALIN+FERT  3.0 lb/A	100
STOMP  4.90 lb/A	100	PENDIMETHALIN+FERT  3.0 lb/A	99	PENDIMETHALIN+FERT3.0 lb/A	100	DIMENSION -G-  0.38 lb/A	99
PRODIAMINE  0.75 lb/A	100	PRODIAMINE  1.0 lb/A	98	PRODIAMINE  1.0 lb/A	100	PRODIAMINE  0.75 lb/A	99
BEST-FERT  3.0 lb/A	100	GALLERY TEAM FERT  375 lb prod./A	98	GALLERY+TEAM FERT 375 lb prod/A	100	PRODIAMINE  1.0 lb/A	98
RONSTAR  3.0 lb/A	100	RONSTAR  3.0 lb/A	98	RONSTAR  3.0 lb/A	99	DIMENSION -G-  0.25 lb/A	97
PENDIMETHALIN+FERT  3.0 lb/A	100	DIMENSION -L-  0.50 lb/A	98	DIMENSION -G-  0.25 lb/A	99	GALLERY+TEAM/FERT  375 lb prod./A	96
PENDIMETHALIN EXP  4.90 lb/A	100	DIMENSION -G-  0.25 lb/A	96	BEST-FERT  3.0 lb/A	99	BEST FERT  3.0 lb/A	96
PRODIAMINE  1.0 lb/A	99	BEST FERT  3.0 lb/A	95	PENDIMETHALIN EXP 4.90 lb/A	99	RONSTAR  3.0 lb/A	96
DIMENSION -L-  0.50 lb/A	99	PRODIAMINE  0.75 lb/A	95	DIMENSION -L-  0.50 lb/A	98	DIMENSION -L-  0.50 lb/A	95
GALLERY+TEAM FERT  375 lb prod./A	99	PENDIMETHALIN EXP  4.90 lb/A	92	PENDIMETHALIN FERT 1.5 lb/A	98	STOMP  4.90 lb/A	94
DIMENSION -G-  0.25 lb/A	99	SURFLAN FERT  2 lb/A	92	SURFLAN FERT  2 lb/A	95	SURFLAN FERT  2 lb/A	90
PENDIMETHALIN+FERT  1.5 lb/A	98	PENDIMETHALIN FERT  1.5 lb/A	89	STOMP  4.90 lb/A	94	XL  3.0 lb/A	87
GALLERY TEAM FERT  250 lb prod./A	98	PENDIMETHALIN EXP  2.45 lb/A	88	DIMENSION -L-  0.38 lb/A	93	PRODIAMINE  0.5 lb/A	86
PRODIAMINE  0.5 lb/A	97	XL  3.0 lb/A	88	XL  3.0 lb/A	92	PENDIMETHALIN EXP  2.45 lb/A	83
SURFLAN AS  1.5 lb/A	96	STOMP  4.90 lb/A	86	PRODIAMINE  0.75 lb/A	91	DIMENSION -L-  0.38 lb/A	81
PENDIMETHALIN EXP  2.45 lb/A	96	DIMENSION -L-  0.38 lb/A	85	PENDIMETHALIN EXP 2.45 lb/A	91	PENDIMETHALIN FERT  1.5 lb/A	80
DIMENSION -L-  0.38 lb/A	95	PRODIAMINE  0.5 lb/A	84	PRODIAMINE  O.5 lb/A	86	PENDIMETHALIN EXP  4.90 lb/A	69
SURFLAN FERT  2 lb/A	95	GALLERY+TEAM FERT  250 lb prod./A	80	QUINCLORAC+MSMA1 0.5+2 lb/A	71	GALLERY+TEAM/FERT  250 lb prod./A	68
XL  3.0 lb/A	93	STOMP  2.45 lb/A	75	SURFLAN AS  2.0 lb/A	70	SURFLAN AS  2.0 lb/A	63
STOMP  2.45 lb/A	90	BEST FERT  1.5 lb/A	73	STOMP  2.45 lb/A	70	QUINCLORAC+MSMA2 0.5+2 lb/A	58
XL  1.5 lb/A	87	SURFLAN AS  1.5 lb/A	67	XL  1.5 lb/A	66	STOMP  2.45 lb/A	52
BEST FERT  1.5 lb/A	85	SURFLAN AS  2.0 lb/A	59	GALLERY+TEAM FERT 250 lb prod/A	62	SURFLAN AS  1.5 lb/A	49
GALLERY+SURF/FERT  233 lb prod./A	80	XL  1.5 lb/A	42	GALLERY+SURF FERT 233 lb prod/A	51	GALLERY+SURF/FERT  233 lb prod./A	41
SURFLAN AS  2.0 lb/A	65	GALLERY+SURF FERT  233 lb prod/A	36	SURFLAN AS  1.5 lb/A	50	BEST FERT  1.5 lb/A	40
DIMENSION -L-  0.125 lb/A	47	DIMENSION -L-  0.125 lb/A	13	BEST-FERT  1.5 lb/A	46	XL  1.5 lb/A	14
				DIMENSION -L-  0.125 lb/A	12	DIMENSION -L-  0.125 lb/A	0
				SURFLAN ILLOXAN1 1+0.5 lb/A	0	SURFLAN+ILLOXAN2 1+0.5 lb/A	0

Note: These treatments were not applied until July 8, 1993.

¹Days after treatment (DAT) for these products was 39 on August 16, 1993.

²Days after treatment (DAT) for these products was 76 on September 22, 1993.

Appendix A. Herbicide treatments used to control southwest cupgrass. University of Arizona 1993.

Name Formulation Rate ai/A Pre/Post

Surflan/Fert. 1.00 GR 2.00 Pre

Surflan A.S. 4.00 SC 1.50* Pre

Surflan A.S. 4.00 SC 2.00 Pre

Gallery-Surflan/Fert. 1.15 GR 233 lb prod/A Pre

Gallery-Team/Fert. 1.09 GR 150 lb prod/A Pre

Gallery-Team/Fert. 1.09 GR 375 lb prod/A Pre

XL 2.00 GR 1.50* Pre

XL 2.00 GR 3.00 Pre

Ronstar 2.00 GR 3.00 Pre

Pendimethalin/Fert. 0.75 % GR 1.50* Pre

Pendimethalin/Fert. 0.75% GR 3.00 Pre

Stomp 60 DG 2.45 Pre

Stomp 60 DG 4.90 Pre

Pendimethalin Exp. GR 60 DG 2.45 Pre

Pendimethalin Exp. GR 60 DG 4.90 Pre

Best Fert./Team 1.15 GR 1.50* Pre

Best Fert./Team 1.15 GR 3.00 Pre

Dimension Clay GR 0.25% GR 0.25 Pre

Dimension Clay GR 0.25% GR 0.38 Pre

Dimension Clay GR 0.25% GR 0.50 Pre

Dithiopyr 1.00 EC 0.125 Pre

Dithiopyr 1.00 EC 0.38 Pre

Dithiopyr 1.00 EC 0.50 Pre

Prodiamine 65 WP 0.50 Pre

Prodiamine 65 WP 0.75 Pre

Prodiamine 65 WP 1.00 Pre

Surflan A.S. 4.00 SC 1.00 Post

+ Illoxan 3.00 EC 0.50

Quinclorac 75% 0.50

+ BASF 0900 25 0.25% v/v Post

+ MSMA 6.00 EC 2.00