Malheur Experiment Station
Oregon State University
Information for Sustainable Agriculture

EVALUATION OF PROWL H2O®, SANDEA®, AND TARGA® FOR

WEED CONTROL IN ALFALFA

Joel Felix and Joey Ishida

Malheur Experiment Station

Oregon State University

Ontario, OR, 2009

Introduction

The importance of weed control in alfalfa can not be overemphasized, considering the high investment and value associated with the crop. If not controlled in a timely fashion or if allowed to compete with alfalfa, weeds will reduce available moisture, nutrients, sunlight, and negatively impact hay yield and quality. Weeds have also been implicated in causing premature alfalfa stand loss by harboring and increasing disease and insect incidences.

One of the goals of this study was to identify an option for yellow nutsedge control in alfalfa. The specific objective was to evaluate alfalfa injury and weed control from halosulfuron and pendimethalin (Sandea® and Prowl® H2O) when applied after the first hay cut to established alfalfa. Sandea is very effective on yellow nutsedge and may provide needed control in fields planted to alfalfa. Another use for Sandea is to provide yellow nutsedge control along field edges in order to minimize sedge expansion into areas surrounding alfalfa plantations. The herbicide also provided excellent control of pigweeds. It is important to recognize that Sandea is not registered, but Prowl H2O is registered for weed control in established alfalfa.

Materials and Methods

The study was conducted in a field near the Malheur Experiment Station, Ontario, Oregon in 2009. Treatments were arranged in a randomized complete block design with four replications. On May 8, chlorpyrifos (Lorsban®-4E) was applied at 0.5 lb. ai/acre (16 oz./acre) to control alfalfa weevil. First alfalfa forage cut was on June 2 and immediately placed in the greenhouse to dry before being weighed to determine hay yield. Herbicide treatments were applied on June 27 when alfalfa was about 3 inches tall using a CO2-pressurized backpack sprayer with a boom equipped with 8002EVS flat fan nozzles. Visual evaluations for alfalfa injury and weed control were done on July 6, July 13, and August 3, 2009 using a 0-100% scale (where 0% = no crop injury and 100% = complete crop damage). The second and third hay harvests were done on July 30 and September 22. The study was furrow irrigated for 24 hours each on April 20, May 28, June 29, July 24, and August 28. Data were subjected to analysis of variance following appropriate procedures and means compared using the least significant difference (LSD) and P = 0.05. Results are presented in Tables 1 and 2.

Results

Visual evaluations on July 6 indicated high alfalfa injury from Sandea treatments (Table 1). Visual injury ranged from 72 to 90 percent and increased with rate. Injury symptoms were characterized by shortening of the internodes and general lack of growth (stunted growth) on sprayed stems. The injury increased with rate increase and was exacerbated by inclusion of a nonionic surfactant (NIS). Alfalfa injury was still very high on July 13, ranging from 68 to 77 percent, again increasing as herbicide rate increased. Visual evaluations on August 3, 2009 indicated alfalfa injury ranging from 5 to 8 percent. The sprayed stems were able to develop new healthy shoots, which helped create a full canopy cover over time. Application of Prowl H2O and Targa® did not injure alfalfa.

Average alfalfa yield for the second cutting was reduced 19 percent by all Sandea treatments compared to Prowl H2O applied at 4.2 pt./acre and 2.1 pt. + Raptor at 4 fl. oz./acre (Table 2) reflecting the high injury rate observed earlier. However, there was no difference between treatments for the final alfalfa cutting in September. As a response to reduced growth, most plants initiated new shoots and the canopy was able to close by the time the second cut was done. More tests are needed to determine the timing and fitness of Sandea into established alfalfa fields. Sandea may provide needed yellow nutsedge control along alfalfa field edges to curtail expansion into neighboring fields.


Table 1. Alfalfa variety hay yield and third-cutting crude protein, ADF, NDF, and RFQ for 2009.  Oregon State University, Malheur Experiment Station, Ontario, OR.

 

 

Cutting date

2009

Crude

 

 

 

Variety

5/27

7/09

8/12

10/01

 

total

protein

ADFa

NDFb

RFQc

 

------------------ton/acred----------------

-------% of DWe-------

 

FC 2055

1.89

3.25

1.81

1.81

 

8.76

23.6

32.8

37.2

187.4

Masterpiece

1.87

3.25

1.69

1.84

 

8.65

23.8

31.6

36.2

196.8

Rustler II

1.87

3.14

1.84

1.73

 

8.58

23.6

32.2

36.4

192.2

FC 1055

1.82

2.95

1.8

1.81

 

8.38

23.2

32.8

37.2

189.6

Lahontan

1.72

3.05

1.64

1.61

 

8.02

22.2

33.2

38

177.8

DKA-42-15

1.9

2.56

1.79

1.73

 

7.98

24.2

30.4

35

202.6

FC 1045

1.78

3.04

1.57

1.57

 

7.96

23.4

33

38.2

182.2

WL 357 HQ

1.84

2.85

1.65

1.48

 

7.82

23.4

32.4

37.4

185

WL 319 HQ

1.65

3.03

1.57

1.42

 

7.67

24

30.8

34.8

202

Wrangler

1.66

2.58

1.42

1.5

 

7.16

23.6

32.2

36.4

194.8

Mean

1.80

3.02

1.69

1.65

 

8.10

23.5

32.1

36.7

191.0

LSD (0.05)

0.24

0.14

0.11

0.13

 

0.36

NSf

1.44

1.64

13.39

aADF: acid detergent fiber. bNDF: neutral detergent fiber. cRFQ: relative forage quality. dYield at 88 percent dry matter. eDW: dry weight. fNS: Not Significant at the alpha = 0.05 level.

 

Table 2. Alfalfa variety hay yield in each of the first 4 years, and cumulative total yield in the 2006-2011 furrow irrigated forage variety trial.  Oregon State University, Malheur Experiment Station, Ontario, OR, 2009.

 

 

2006

2007

2008

2009

Cumulative

Variety

total

total

total

total

total

--------------  ton/acrea  ------------

DKA-42-15

7.1

7.8

6.61

8.76

30.27

Masterpiece

7

8

6.54

8.65

30.19

FC 2055

6.9

7.9

6.7

7.98

29.48

WL 357 HQ

6.9

8.3

6.41

7.82

29.43

FC 1045

6.9

7.6

6.26

8.58

29.34

Rustler II

7.1

7.6

6.53

7.96

29.19

FC 1055

6.7

7.6

6.45

8.38

29.13

WL 319 HQ

7

8

6.3

7.67

28.97

Wrangler

6.5

7.3

6.27

8.02

28.09

Lahontan

6.8

7.1

6.13

7.16

27.19

Mean

6.9

7.7

6.42

8.10

29.13

LSD (0.05)

NSb

0.36

NS

0.36

0.60

                  aYield at 88 percent dry matter. bNS: Not significant at the alpha = 0.05 level.

 

 

 

Table 3. Variety source, year of release, fall dormancy, and level of resistance to pests and diseases for alfalfa varieties in the 2006-2011 furrow-irrigated forage variety trial.  Oregon State University, Malheur Experiment Station, Ontario, OR, 2009.

 

 

 

Release

 

Pest resistance ratingb

Variety

Source

year

FDa

BW

FW

VW

PRR

AN

SAA

PA

SN

AP

RKN

Lahontan

public

1954

6c

MR

LR

-

LR

-

MR

LR

R

-

-

Wrangler

public

1984

2

MR

R

LR

HR

LR

HR

HR

LR

LR

LR

Rustler II

Andrews Seed

1995

4

HR

HR

HR

HR

HR

R

HR

MR

R

-

Masterpiece

Simplot

2000

4

HR

HR

R

HR

HR

R

-

HR

R

R

DKA-42-15

Monsanto

2001

4

HR

HR

HR

HR

HR

R

HR

R

HR

-

WL 319 HQ

W-L Research

2002

3

HR

HR

HR

HR

HR

R

HR

MR

HR

LR

WL 357 HQ

W-L Research

2003

5

HR

HR

HR

HR

HR

R

R

MR

HR

LR

FC 1045

Andrews Seed

2005

4

HR

HR

HR

HR

HR

MR

R

R

R

MR

FC 1055

Andrews Seed

2006

5

HR

HR

HR

HR

R

R

R

HR

R

HR

FC 2055

Andrews Seed

2006

5

HR

HR

HR

HR

R

R

R

HR

R

HR

aFD: fall dormancy, BW: bacterial wilt, FW: Fusarium wilt, VW: Verticillium wilt, PRR: Phytophthora root rot, AN: Anthracnose, SAA: spotted alfalfa aphid, PA: pea aphid, SN: stem nematode, AP: Aphanomyces, RKN: Northern root knot nematode.

 

bPest resistance rating: >50 percent = HR (high resistance), 31-50 percent = R (resistant),

15-30 percent = MR (moderate resistance), 6-14 percent = LR (low resistance).

 

cFall dormancy: 1 = Norseman, 2 = Vernal, 3 = Ranger, 4 = Saranac, 5 = DuPuits, 6 = Lahontan.

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Last updated  Tuesday July 19, 2011.


Cite As:

Felix, J. and J. Ishida. 2010. Evaluation of Prowl H2O®, Sandea®, and Targa® for  Weed Control in Alfalfa, Oregon State University Agricultural Experiment Station.  p 14-17. In Shock C.C. (Ed.) Oregon State University Agricultural Experiment Station, Malheur Experiment Station Annual Report 2009, Department of Crop and Soil Science Ext/CrS 131.