Native Forb and Milestone Orb and Shrub Tolerance Ilestone Herbicide

Native Forb and Shrub Tolerance to Milestone ® Herbicide

Milestone ® (aminopyralid) is a broadleaf herbicide that has reduced risk to the environment compared with other commercially available herbicides, making it a desirable alternative for invasive weed control on rangeland and wildland sites. Effect of Milestone on desirable native forbs and shrubs is a consideration for land managers when making decisions about controlling invasive plants. Exp eriments were established at 16 locations in 6 states to determine long -term response of native forbs and shrubs to Milestone ® applied in summ er or fall, and to develop a tolerance/susceptibility ranking for native plants. Studies were established within diverse native plant communities in western Montana; Boulder and Steamboat , Colorado; Theodore Roosevelt National Park (TRNP), North Dakota; Glacial Ridge Preserve and restored prairies in M innesota; South Dakota Fish and Game, and o pen grassland near Grangeville, Idaho .

This is a summary of multiple research locations completed by Mary Halstvedt, Dow AgroSciences Field Scientist . The follo wing researchers conducted the field experiments: Travis Almquist, Luke Samuel, Rodney Lym, North Dakota State University, Fargo; K. George Beck, Colorado State University, Ft. Collins; Roger Becker, University of Minnesota, St. Paul; Celestine Duncan, Weed Management Services, Helena, MT; Pat Green, US Forest Service Ecologist (Retired) ID; Michael Moechnig, South Dakota State University; and Peter Rice, University of Montana, Missoula.

Materials and Methods: Plant communities with high levels of diversity were selected as research sites. Some locations had light to moderate infestations of invasive species such as Canada thistle , yellow starthistle, or spotted knapweed . Field experiments were designed as randomized complete block with two to five replications per treatment and initiated from 2004 to 2009. Herbicide treatments were Milestone ® at 5 or 7 fluid ounces/A . Broadcast ground applications were made with either a CO 2 backpack sprayer, or pickup boom sprayer. At one M ontana location a broadcast application was made with a helicopter. Treatments were made in late season (August/September/Oct ober) at seven locations, June /July at four locations, and June and September comparisons at two Minnesota and Colorado sites , and South Dakota.

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Data collection across sites varied and included either canopy cover or plant counts along a permanent transect, or plant density within each plot.

Table 1: Research Locations and Methods: Location Name Researcher Site Type Treatment Time Methods Code Rod Lym and Luke Milestone ® Pre and Post: 30 plots - 3 Theadore Roosevelt Western ND Canada thistle/arid October Samuel, North Dakota at 7 fluid frames/plot - 90 frames National Park USFS ND grassland 2004 State University oz/A per treatment Two Rivers and Post only: 20 frames per Milestone ® June and Hedquist- MN Dept of Southwest Roger Becker, Canada thistle prairie treatment for counts by at 5 fluid September Natural MN 2008 University of Minnesota restoration species and presence oz/A 2006 Resources(DNR) per plot Rod Lym and Travis Milestone ® Pre and Post: 90 frames Glacial Ridge Nature Northern MN Canada thistle prairie October Almquist, North Dakota at 7 fluid per treatment % cover by Conservancy GlacialRidge restoration 2006 SU oz/A species Open canopy, Larry Creek Bitterroot Western MT Peter Rice, University commercially thinned National Forest MTRice of Montana Ponderosa pine with Pre and Post: 5 reps - 4 spotted knapweed transects with 9 frames - Milestone ® Grant Cr. Elk Refuge Rough fescue October 180 frames per Western MT at 5 fluid National Wildlife Peter Rice grassland with spotted 2006 treatment. Canopy cover MTRice oz/A Federation knapweed and frequency of Open canopy, occurance Pattee Canyon Lolo Western MT Peter Rice Ponderosa pine habitat National Forest MTRice with spotted knapweed George Beck and Jim ® Pre and post data - Boulder, CO Diffuse knapweed Milestone Boulder Open Space Sebastian, Colorado June 2007 density of each species CO2007 upland rangeland at 5 fluid State University oz/A per plot. Celestine Duncan, ® Native rangeland with Helena, MT Native Rangeland Milestone Pre and post canopy Weed Management June 2007 good forb diversity MTDuncan weed free at 5 fluid cover by species Services oz/A Milestone ® Celestine Duncan and at 5 fluid Montana USFS Aerial Western MT Spotted knapweed October Pre and post canopy Andy Kulla, US Forest oz/A Operational Study USFSMT open canopy forest 2007 cover by species Service applied by helicopter Pre and Post: 5 reps - 4 Native bunchgrass and Milestone ® transects with 9 frames - Missoula, MT Peter Rice, University forb plant community Mount Sentinel at 7 fluid June 2008 180 frames per MTRice08 of Montana with moderate spotted oz/A treatment. Canopy cover knapweed infestation by species. Kufrin Waterfowl Plant counts taken per Morris Wetland Production Area Milestone ® June and Ortonville, MN Roger Becker, square yard for each Management Distirct Canada thistle control at 5 fluid September MNKufrin University of Minnesota species and % visual US Fish and Wildlife in 2 year old prairie oz/A 2006 cover by species restoration

Native rangeland in George Beck and Jim Milestone ® July and Pre and post data - Steamboat, High elevation (8200 Western Colorado - 2 Sebastian, Colorado at 7 fluid September density of each species CO2009 feet) native rangeland locations State University oz/A 2009 per plot.

Pat Green, US Forest Milestone ® Pre and post canopy Open grassland in Grangeville Native rangeland with August Service Ecologist at 5 fluid cover by species - 4 North Central Idaho IDGreen yellow starthistle 2009 (Retired) oz/A transects with 9 frames

Micheal Moechnig, Milestone ® July and South Dakota Fish Big Stone, SD % Visual canopy cover by South Dakota State Native Prairie at 7 fluid September and Game SD2009 species University oz/A 2009 ®Trademark of Dow AgroSciences LLC

First year post-application vegetation sampling was conducted in June and July the summer after treatment at all locations. Second year sampling was completed at 14 study sites. Individual rankings of tolerance to Milestone ® were established for 90 native forb species and 19 shrubs. Many species will show transient symptoms the year of treatment and those observations were not quantified.

Evaluations were the year following treatment and were based on individual species reduction in canopy cover or density compared to non -treated controls or baseline data .

Table 2: Four categories were developed for ranking tolerance of forbs an d shrubs to Milestone ® herbicide: Code Category Symptoms Injury Level Minimal symptoms <15% injury - may have Tolerant <15% T slight cupping of leaves Symptoms include cupping/yellowing and can MT Moderately tolerant inhibit flowering, with recovery the first growing 15 to 50% stand reduction season after application Injury could be significant the first year and may Moderately susceptible 51 to 75% stand reduction MS reduce stand Severe injury the season of application and stand reduction the year after treatment with Susceptible >75% stand reduction S possible death of established plants. Some plants may regenerate from seed bank Copyright 2012 Dow AgroSciences LLC

Of the 90 forb species categorized, 23, 14, 19, and 34 were ranked susceptible (S), moderately susceptible (MS) , moderately tolerant (MT), and tolerant (T) , respectively at one year after application. Many forbs recovered by the second year following Milestone ® application with only 1 9 of 90 native forbs ranked either MS or S (Figure 1). Sunflower, yarrow, and lobelia were very susceptible to Milestone ® while lupine, golden Alexander and wild bergamot were very tolerant.

Figure 1: Results of 90 f orb species with both 1 and 2 YAT (year after treatment) data showing increase in species tolerance by the second year following treatment.

There were 29 plant families represented, with the greatest number of species (35%) in the Asteraceae family.

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Table 3: Tolerance rankings of forb species to Milestone ® herbicide. Forbs are listed alphabetically by common name within plant family and rankings are shown for 1 and 2 years after treatment (YAT). See Table 1 and 2 for locations and category description. Appl Common Name Family Genus Species 1 YAT 2 YAT Time Location Golden Alexanders Apiaceae Zizia aurea TT Fall Glacial Ridge Golden Alexanders Apiaceae Zizia aurea TT Summer MNKufrin Hearl-leaved alexanders Apiaceae Zizia aptera T NA Both MN2008 Nine-leaf lomatium Apiaceae Lomatium triternatum MTT Fall MTRice Wyeth's biscuitroot Apiaceae Lomatium ambiguum TT Fall MTRice Spreading dogbane Apocynaceae Apocynum androsaemifolium TT Fall Glacial Ridge Common milkweed Asclepiadaceae Asclepias syriaca TT Fall Glacial Ridge Arrowleaf balsamroot Asteraceae Balsamorhiza sagittata MS MT Fall MTRice Arrowleaf balsamroot Asteraceae Balsamorhiza sagittata MS+ MT+ Summer MTRice08 Black-eyed Susan Asteraceae Rudbeckia hirta S NA Both MN2008 Blanket flower Asteraceae Gaillardia aristata MTT Both MT Rice/Glacial/MTRice08 Canada goldenrod Asteraceae Solidago canadensis MT+ NA Summer SD/MN Kufrin Canada goldenrod Asteraceae Solidago canadensis MS MS Fall Glacial Ridge,MNKufrin cudweed sage Asteraceae Artemesia ludoviciana TT Summer MTDuncan Cup plant Asteraceae Silphium perfoliatum MT NA Both MN2008 Daisy fleabane Asteraceae Erigeron strigosus MT NA Both MN2008 Gay feather Asteraceae Liatris punctata TT Summer CO2007 Giant goldenrod Asteraceae Solidago gigantea MT NA Both MN2008 Giant sunflower Asteraceae Helianthus giganteus S MS Fall Glacial Ridge Gumweed Asteraceae Grindelia squarrosa MS MT Fall MTRice Hairy golden aster Asteraceae Chrysopsis villosa MTT Both MT Rice/MT Duncan Heath aster Asteraceae Aster ericoides MT NA Both MN2008 Hound's tongue hawkweed Asteraceae Hieracium cynoglossoides MT MT Fall MTRice Little sunflower Asteraceae Helianthus pumilus MS MT Summer CO07/CO09 Little sunflower Asteraceae Helianthus pumilus T NA Fall CO09 Maximilian sunflower Asteraceae Helianthus maximiliani SS Fall Glacial Ridge Missouri goldenrod Asteraceae Solidago missouriensis MTT Fall MTRice Nuttall's pussy-toes Asteraceae Antennaria parviflora MS MT Fall MT Rice Nuttall's pussy-toes Asteraceae Antennaria parviflora S MS Summer MT Duncan Orange arnica Asteraceae Arnica fulgens SS Fall MTRice Panicled aster Asteraceae Aster lanceolatum MT NA Both MN2008 Prairie blazingstar Asteraceae Liatris aspera MT NA Both MN2008 Prairie goldenrod Asteraceae Solidago missouriensis MS MT Fall Glacial Ridge Prairie sunflower Asteraceae Helianthus pauciflorus MS NA Fall Glacial Ridge, MN Rosy pussy-toes Asteraceae Antennaria microphylla MTT Fall MTRice Shaggy fleabane Asteraceae Erigeron pumulis MTT Fall MTRice Smooth Blue aster Asteraceae Aster laeve MT NA Both MN2008 Stiff goldenrod Asteraceae Solidago rigida MT NA Summer MN2008 Stiff goldenrod Asteraceae Solidago rigida S NA Fall MNKufrin Stiff sunflower Asteraceae Helianthus pauciflorus MT NA Summer SD Stiff sunflower Asteraceae Helianthus pauciflorus MS MT Fall Glacial Ridge Sweet clover Asteraceae Melilotus officinalis ST Fall Glacial Ridge Sweet smooth oxeye Asteraceae Heliopsis helianthoides MT NA Both MN2008 Tall sunflower Asteraceae Helianthus giganteus S NA Both MN2008 White panicle aster Asteraceae Aster simplex S MT Fall Glacial Ridge White prairie aster Asteraceae Aster ericoides MS NA Summer SD White prairie aster Asteraceae Aster ericoides MT MT Fall Glacial Ridge/SD Yarrow Asteraceae Achillea millefolium SS Both MTRice/MTRice08 Yellow prairie coneflower Asteraceae Ratibida pinnata S NA Both MN2008 Wayside gromwell Boraginaceae Lithospermum ruderale MT MT Fall MTRice Alyssum Brassicaceae Alyssum alyssoides TT Summer MTDuncan Nuttall's rockress Brassicaceae Arabis nuttallii TT Fall MTRice Palespike lobelia Campanulaceae Lobelia spicata SS Fall Glacial Ridge Field chickweed Caryophyllaceae Cerastium arvense MS MT Fall MTRice Jagged chickweed Caryophyllaceae Holosteum umbellatum ST Fall MTRice threadleaf sandwort Caryophyllaceae Arenaria capillaris S MT Summer MTDuncan Table 3: Continued

Appl Common Name Family Genus Species 1 YAT 2 YAT Time Location Prairie spiderwort Commelinaceae Tradescantia occidentalis MS NA Both MN2008 Dwarf morning glory Convolvulaceae Ipomoea tricolor MTT Summer CO2007 Equisetum Equisetaceae Equisetum arvense T NA Both MN2008 Flowering spurge Euphorbacae Euphorbia corollata T NA Both MN2008 Robust spurge Euphorbia Tithymalus brachyceras TT Summer CO2007 Lupine Fabaceae Lupinus sericeus TT Fall MT Rice Lupine Fabaceae Lupinus sericeus MTT Summer CO2009/MTRice08 Purple prairie clover Fabaceae Dalea purpurea S MS Fall Glacial Ridge Purple prairie clover Fabaceae Dalea purpurea T NA Summer MNKufrin Round-headed bush clover Fabaceae Lespedeza capitata MS NA Both MN2008 Showy tickfoil Fabaceae Desmodium canadense MS NA Both MN2008 Silky prairie clover Fabaceae Petalostemum villosum MS NA Both MN2008 Slimflower scurfpea Fabaceae Psoralea lanceolata S MT Summer CO2007 Trailing wild bean Fabaceae Strophostyles helvola T NA Both MN2008 Weedy milkvetch Fabaceae Astragalus miser S MS Fall MTRice White prairie clover Fabaceae Dalea candida SS Fall Glacial Ridge White wild indigo Fabaceae Baptisia alba MT NA Both MN2008 American water horehound Lamiaceae Lycopus americanus TT Fall Glacial Ridge Hedgenettle Lamiaceae Stachys palustris TT Both Glacial Ridge Horsemint Lamiaceae Monarda fistula TT Fall MTRice Spearmint Lamiaceae Mentha spicata MT NA Summer CO2009 Spearmint Lamiaceae Mentha spicata S NA Fall CO2010 Wild bergamot Lamiaceae Monarda fistulosa TT Both Glacial Ridge/MNKufrin Wild mint Lamiaceae Mentha arvensis TT Fall Glacial Ridge Death camas Lilaceae Zigadenus venenosus TT Both MTRice/MTRice08 Yellow bell Lilaceae Fritillaria pudica TT Both MTRice/MTRice08 Prairie onion Liliaceae Allium stellatum T NA Both MN2008 Sand lilly Lillaceae Leucocrinum montanum MS MT Summer CO2007 Blue flax Linaceae Linum lewisii S MS Summer CO2007 Common primrose Onagraceae Oenothera biennis S NA Both MN2008 Evening Primrose Onagraceae Oenothera howardii MS MT Summer CO2007 Scarlet beeblossum Onagraceae Gaura coccinea S MT Summer CO2007 Tall annual willow-herb Onagraceae Epilobium paniculatum S MS Fall MTRice Yellow woodsorel Oxalidaceae Oxalis stricta TT Fall Glacial Ridge Narrow-leaf collomia Polemoniaceae Collomia linearis S MS Fall MTRice Pink microsteris Polemoniaceae Microsteris gracilis TT Fall MTRice Douglas's knotweed Polygonaceae Polygonun douglasii TT Fall MTRice Pale dock Polygonaceae Rumex altissimus S NA Both MN2008 Subalpine buckwheat Polygonaceae Eriogonum subalpinum S NA Summer CO2009 Subalpine buckwheat Polygonaceae Eriogonum subalpinum MT NA Fall CO2010 Water smartweed Polygonaceae Polygonum amphibium MST Fall Glacial Ridge Winged buckwheat Polygonaceae Pterogonum alatum SS Summer CO2007 Western androsace Primulaceae Androsace occidentalis MST Fall MTRice Purple meadow-rue Ranunculaceae Thalictrum dasycarpum MT MT Fall Glacial Ridge Prairie cinquefoil Rosaceae Potentila arguta S NA Both MN2008 Prairie smoke Rosaceae Geum triflorum MTT Fall MTRice Soft cinquefoil Rosaceae Potentilla gracilis S MT Fall MTRice Soft cinquefoil Rosaceae Potentilla gracilis TT Both CO2009 Virginia strawberry Rosaceae Fragaria virginiana TT Fall MTRice wild rose Rosaceae Rosa sp. S NA Summer MTDuncan Small-flowered fringecup Saxifragaceae Lithophragma parviflora S MS Both MTRice/MTRice08 Yellow Paintbursh Scorphulariaceae Castilleja occidentallis TT Both CO2009 Blue-eyed Mary Scrophulariaceae Collinsia parviflora TT Both MTRice/MTRice08 One-sided penstemon Scrophulariaceae Penstemon secundiflorus MT MT Summer CO2007 Clammy groundcherry Solanaceae Physalis heterophylla S NA Both MN2008 Stinging nettle Urticaceae Urtica dioica MT NA Both MN2008 Blue vervain Verbenaceae Verbena hastata T NA Both MN2008 Hoary vervain Verbenaceae Verbena stricta T NA Both MN2008 Nuttalls violet Violaceae Viola nuttallii MST Summer CO2007

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Sh rubs were more tolerant than forbs to Milestone ®. There were 19 shrub species, and 74% were ranked either MT or T. Shrubs in the Rosaceae Family were generally the most susceptible to Milestone ®.

Table 4: Tolerance of shrub species to Milestone ® herbicide. Rankings include: T=tolerant; MT moderately tolerant; MS moderately susceptible; and S= susceptible (see Table 2 for category description)

Common Name Family Genus Species 1 YAT Location Yucca Agavaceae Yucca glauca T CO-Summer Dogbane Apocynaceae Apocynum andro MT USFS MT Big Sagebrush Asteraceae Artemisia tridentata T Wyoming Summer Fringe sage Asteraceae Artemesia frigida MS CO-Summer Louisiana sage Asteraceae Artemesia ludovicia MS CO-Summer Silver sagebrush Asteraceae Artemisia cana T USFS ND Fall White sagebrush Asteraceae Artemisia ludoviciana T USFS ND Fall Oregon Grape Berberidaceae Berberis repens T USFS MT Elderberry Caprifoliaceae Sambucus racemosa T USFS MT Western snowberry Caprifoliaceae Symphoricarpos occidentalis T USFS ND Fall, USFS MT Buffaloberry Elaeagnaceae Shepherdia canadensis MT USFS MT Silver Buffaloberry Elaeagnaceae Shepherdia argentea T USFS ND Fall Kinnikinnick Ericaceae Arctostaphalos uvaursi T USFS MT Buckbrush Rhamnaceae Ceanothus velutinus T USFS MT Chokecherry Rosaceae Prunus virginiana MT USFS ND Fall, USFS MT Nine-bark Rosaceae Physorcarpus mon S USFS MT Serviceberry Rosaceae Amelancheir alnifolia S USFS MT Wood's rose Rosaceae Rosa woodsii S CO-Summer, USFS MT Golden current Saxifragaceae Ribes aureum T USFS ND Fall

Conclusions: Most native forb species and shrubs were moderately tolerant to tolerant, or recovered following treatment with Milestone ® herbicide. Historical data 1 suggests that by the third or fourth year post -application there would be little difference in non-target forb tolerance with only a few very sensitive forbs being adversely impacted in the long term . Land managers can use these data as a guideline to eva luate risk to native plant communities when using Milestone ® for invasive species management . Milestone ® Herbicide (aminopyralid ) can be used to manage invasive plants in mixed plant communities and facilitate recovery of desirable forbs and shrubs.

1 Rice, P. M., J. C. Toney, D. J. Bedunah, and C. E. Carlson. 1997. Plant community diversity and growth form responses to herbicide applications for control of Centaurea maculosa . J. Appl. Ecol. 34:1397 -1412

This information should only be used as a guideline, environmental situations can vary. To obtain an electronic copy of this report or for more information on invasive weed management, go to techlinenews.com

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