UNL CropWatch June 16, 2010: Controlling Scouringrush

UNL CropWatch June 16, 2010: Controlling Scouringrush

Scouringrush

Figure 1. Scouringrush invading a corn field from a waterway. Scouringrush patches may have stem densities of up to 100 stems per square foot.

Photo - Scouringrush

Figure 2. New scouringrush shoots growing from the rhizome of a parent plant.

June 16, 2010

Photo - Scouringrush cone

Spore-producing cone that forms on the top of a scouringrush stem in
mid summer.

Scouringrush (Equisetum hyemale) is a prehistoric plant that is being reported as a problem weed by many corn and soybean growers in eastern Nebraska. It grows along streams, waterways, and other moist areas, but can spread from these wet areas into the drier soils of fields and pastures (Figure 1). It forms dense patches with up to 350 stems in a 2.5 ft2 area. Stands this dense will interfere with planting, choke out crops, and reduce grain or harvestable forage yields.

Scouringrush is closely related to ferns and is believed to date back about 280-345 million years. It is in the Equisetum (horsetail) family. It is a perennial and has hollow green stems that grows to a height of 2-4 feet (Figure 2). The stems are segmented, stove pipe-like in appearance, and easily pulled apart at the nodes. Normally there are no branches or leaves, although some branching may occur at the nodes if the stems are damaged by mowing or certain chemical treatments. A spore-producing cone (Figure 3) that is yellow to brown forms at the top of the stem mid summer. Scouringrush has deep fibrous roots and extensive rhizomes. It spreads primarily by rhizome, although the spores are also believed to be fertile.

Scouringrush is called by many different names, including snake grass, jointed grass, horsetail and horsepipes. It gets its official name because its rough stem was used by pioneers to scour pans. The stems contain high levels of silica. Livestock that graze it heavily may experience scours, paralysis, abortion, and in rare cases, death.

Nebraska Herbicide Management Trials

We conducted research measuring scouringrush response to herbicides, mowing, and tillage in 2006-2008. We evaluated 24 herbicide active ingredients, individually or in various combinations, but only two (chlorsulfuron and dichlobenil) provided commercially acceptable control of scouringrush (Tables 1-3). Unfortunately, neither chlorsulfuron nor dichlobenil is labeled for use in corn or soybean.

Chlorsulfuron, labeled as Glean for use in wheat, or as Telar for use in non-crop areas, was very effective at controlling scouringrush for more than one year when it was applied at 3 oz /ac. Chlorsulfuron has a long soil residual and can cause significant injury to corn and soybean. The maximum use rate in wheat is 0.33 oz/ac (approximately 10 times less than what we applied), and the rotation interval to corn or soybean is 24 months. If chlorsulfuron were used to control a scouringrush patch that is expanding from a non-crop area into a corn or soybean field, only plant an IR-corn or STS soybean in the treated area in the subsequent three to five years. Even at that, you may still suffer some crop injury from herbicide carryover.

Table 1. A herbicide screen using products labeled for corn, soybean or wheat was conducted on a scouringrush patch near Murdock, Nebr. Treatment solutions were applied at 15 gal/ac using a backpack sprayer on July 11, 2006. Visual control of scouringrush was evaluated 65 days after treatment on a scale of “0” (no control) to “100%” (plant death). Each number represents the mean of three replications (n=3). When we returned to the site the following spring (May 2007) the only treatment where scouringrush density was reduced was Glean. We concluded from this that there was little activity on scouringrush from all the other herbicides tested in this trial.

Herbicide (active ingredient, application rate)

Control (%)


Hornet (clopyralid + flumetsulam, 4 oz/ac)  18
Resolve (rimsulfuron, 2 oz/ac) + Accent (nicosulfuron , 0.67 oz/ac) + Distinct (diflufenzopyr + dicamba, 4 oz/ac)  27
 Beacon (primisulfuron, 0.5 oz/ac) + Accent (nicosulfuron, 0.5 oz/ac) + Clarity (dicamba, 4 oz/ac)  18
 Option (foramsulfuron, 1.75 oz/ac) + Distinct (diflufenzopyr + dicamba, 4 oz/ac)  20
 Resolve (rimsulfuron, 2 oz/ac) + Accent (nicosulfuron, 0.67 oz/ac)  25
 Option (foramsulfuron 1.75 oz/ac)  20
 Beacon (primisulfuron, 0.76 oz/ac)  40
 Glean (chlorsulfuron, 1 oz/ac)  52
 Distinct (diflufenzopyr + dicamba, 4 oz/ac)  17
 MCPA Amine (3 pt/ac)  23
 Buctril (bromoxynil , 2 pt/ac)  15
 Reflex (fomesafen, 1 pt/ac)  17
 Liberty (glufosinate, 68 oz/ac)  23
 Roundup Original (glyphosate, 44 oz/ac)  33
 LSD (0.05)  26

Dichlobenil is a herbicide used for weed control around woody plants and herbaceous perennials. It provided excellent control for at least one year; however, dichlobenil is not labeled for use in corn or soybean. It has very high use rates (150 lb/ac), and is most effective when it is incorporated by tillage.

Glyphosate was not effective at controlling scouringrush in our studies (Tables 1 and 2), and this is consistent with glyphosate performance on other Equisetum species (Torstensson and Borjesson. 2004. Pest Management Science 60:565-569).

Tillage Management

Tilling an area will reduce stem and biomass measurements temporarily, but if other control tactics are not used, the stand will soon regain its earlier density. Repeatedly mowing an area also has little long-term benefit. We have received reports that deep tillage (moldboard plowing) can reduce stands. The best non-chemical approach to controlling scouringrush is likely deep-tilling an area and then immediately planting it to corn or a high population of soybean. Scouringrush is not competitive under dense canopies or in low light conditions. This aggressive management approach will likely need to be repeated for several years to eliminate or minimize a patch.

There are two cautions regarding tillage. First, the benefits of controlling scouringrush using deep tillage should be weighed against the risk of soil erosion along a waterway. Second, tillage, especially shallow tillage, can expand a scouringrush patch. Because scouringrush reproduces primarily by rhizome, if the tillage operation moves the rhizomes beyond the area of the original patch, new plants can form and the patch can grow larger. Scouringrush shoots can form from small sections of rhizomes, even when they are buried 6 inches or more.

Summary

Little information has been reported on scouringrush biology and control. Based on literature describing research on field horsetail (a closely related species) and observations in 2008-2009, we believe that tillage may be more effective if it takes place in the spring or first part of the summer while the shoots are still growing, and herbicides may be more effective after shoots stop growing mid-summer and rhizome growth accelerates. We hope to have more information in future years to share about how to best manage this ancient plant.

Mark Bernards
Extension Weeds Specialist, Lincoln
Eric Frasure

Former Graduate Student, UNL Department of Agronomy and Horticulture
Lowell Sandell
Extension Educator, Weed Science, Lincoln

Table 2.  A herbicide screen using products labeled for corn, soybean, wheat, pasture or non-crop areas was conducted on a scouringrush patch near Murdock, Nebr.  Treatment solutions were applied at 20 gal/acc using a backpack sprayer two times.  The first application occurred on July 6, 2007, and the second application was on August 11, 2007.  Herbicide rates were adjusted up or down depending on the observed efficacy of the first application.  Each of the plots was divided in half, and half the plot was mowed on July 31 and October 31.  Stand density and plant biomass measurements were taken from each plot August 26-27, 2008, one year after the second treatment.   Each number represents the mean of three replications (n=3).  There was no interaction between mowing and herbicide treatment, so data were averaged.  The repeated mowing had no effect on stem count, and reduced biomass only 20%.  Telar had the greatest effect on stem density and biomass.  Arsenal and Oust XP had the second greatest effect.

Herbicide (active ingredient, appl. 1 rate, appl. 2 rate)

Stems
(#/2.5 ft2

Biomass
(g/0.25 m2)


Glean (chlorsulfuron, 3 oz/ac, 1.5 oz/ac)

0

0

Arsenal (imazapyr, 2 pt/ac, 4 pt/ac)

113

147

Oust XP (sulfometuron, 4 oz/ac, 8 oz/ac)

107

112

Permit (halosulfuron, 1.33 oz/ac, 2.66 oz/ac)

203

332

Beacon (primisulfuron, 0.38 oz/ac, 0.76 oz/ac)

244

454

Resolve (rimsulfuron, 1 oz/ac, 2 oz/ac) + Accent (nicosulfuron , 0.67 oz/ac, 1.24 oz/ac) + Peak (prosulfuron, 0.5 oz/ac, 1 oz/ac) + Clarity (dicamba, 16 oz/ac, 32 oz/ac)

190

342

Redeem R&P (triclopyr+clopyralid, 2 pt/ac, 4 pt/ac)

140

261

Tordon 22K (picloram, 1 qt/ac, 2 qt/ac)

132

292

Python (flumetsulam, 0.7 oz/ac, 1.4 oz/ac) + Dual II Magnum (S-metolachlor, 2 pt/ac, 4 pt/ac) + Roundup WeatherMAX (glyphosate, 44 oz/ac, 88 oz/ac)

134

273

Untreated

257

501

LSD (0.05)

48

92


Table 3.  An experiment evaluating different herbicides and cultural control methods was conducted on three scouringrush patches near Plattsmouth, Nebr., in 2008. Herbicides were applied in mid-June or mid-July (depending on location) using a backpack sprayer at 20 gal/ac.  Tillage and mowing treatments were begun mid-June or July, and then repeated August 20 and November 24. Scouringrush stem count and biomass dry weight was measured one year after treatment.  Data represent the mean of three locations and three replications per location.  Telar and Casoron were the most effective treatments for controlling scouringrush.  Repeated tillage (three times) and tillage followed by planting corn were equally effective at controlling scouringrush, reducing stem counts and biomass approximately 50% one year after treatments were established

Treatment (active ingredient, appl. rate)

Stems
(#/0.25m2)

Biomass
(g/0.25m2)


Telar (chlorsulfuron, 3 oz/ac)

0

0

Casoron (dichlobenil, 150 lb/ac)

41

79

Ally XP (metsulfuron, 2 oz/ac)

108

166

MCPA Amine (MCPA, 6 pt/ac)

140

227

Garlon 4 (triclopyr, 3 pt/ac)

153

795

Tillage (3 times)

87

119

Corn (tillage followed by planting corn)

85

138

Mowing (3 times)

217

230

Untreated

179

292

LSD

31

44