GRASSES AS INVASIVE SPECIESClay Antieau, MS, PhC

Botanist, Horticulturist, Environmental Educator

WFCA Eighth Western Native Plant ConferenceNovember 2019

THE GRASS FAMILY (Poaceae)• Genera : 700 – 800

• Species: 7,500 – 11,000 (4th largest)

• Comparable in size to Aves (Birds); ~ twice as large as Mammalia; half the size of Orchid or Aster families

• First appeared in pollen record 55 – 70 mya (Paleocene)

• Only angiosperm family found natively on all seven continents (Deschampsia Antarctica)

• Includes cereal crops (forage, food, sugar, beer...); many ecological dominants

• All major civilizations developed around cultivated grasses (Asia to Middle East to New World)

Among the World’s Worst Invasives: Grasses

• Imperata cylindrica (cogon grass)• Phragmites australis (common reed)• Phalaris arundinacea (reed canarygrass)• Sorghum halepense (Johnson grass)• Spartina species and hybrids (cordgrasses)• Cortaderia species and hybrids (pampas grass)• Arundo donax (giant reed)• Microstegium vimineum (Japanese stilt grass)• Bromus tectorum (cheat)• Taeniatherum caput-medusae (medusahead)• Cynodon dactylon (Bermuda grass)• Neyraudia reynaudiana (silk reed)

Important North American Invasive Grasses(adapted from www.fs.fed.us/database/feis)

Aegilops cylindricus (goat grass)Aegilops triuncialis (barbed goat grass)Agropyron desertorum (desert wheat grass)Agropyron cristatum (crested wheat grass)Ammophila arenaria (European beachgrass) Arrhenatherum elatius (tall oatgrass)Arundo donax (giant reed)Brachypodium sylvaticum (false brome)Bromus hordeaceus (soft chess)Bromus inermis (smooth brome)Bromus japonicus (Japanese brome)Bromus tectorum (cheat)Cortaderia jubatua(pampas grass)Cynodon dactylon (Bermuda grass)Dactylis glomerata (orchard grass)Echinochloa crus-galli (barnyard grass)

Eragrostis curvula (weeping lovegrass)Eragrostis lehmanniana (Lehmann love grass)Elytrigia repens (quack grass)Festuca arundinacea (tall fescue)Imperata cylindrica (cogon grass)Microstegium vimineum (Japanese stilt grass)Oplismenus undulatifolius (wavyleaf basket grass)Pennisetum setaceum (fountain grass)Phalaris arundinacea (reed canarygrass)Phalaris aquatica (Harding grass)Poa pratensis (Kentucky bluegrass)Ripidium ravennae (ravenna grass) Sorghum halepense (Johnson grass)Spartina alterniflora (smooth cordgrass)Taeniatherum caput-medusae(medusahead)

Cogon grass (Imperata cylindrica)

Cogon grass (Imperata cylindrica)• Infests more than 500 million acres worldwide; every continent except Antarctica; expanding….

• USA introductions: accidental (crate packing) [1911, Mobile (Grand Bay), AL] and intentional (forage) (1921 MS; 1930 FL)

rhizomes: > 60% of total biomass(40 tons/ac); up to 4 feet deep

Cogon grass (Imperata cylindrica)

Ornamental cultivar ‘Red Baron’ can revert back to the wild form and cause infestations.

Japanese stilt grass (Microstegium vimineum)Chris Evans, Illinois Wildlife Action Plan, Bugwood.org

Giant reed (Arundo donax), Sabino Canyon, AZphoto by Mark Hengesbaugh

VENTENATA(Ventenata dubia)

photos by Matt Lavin

•Annual grass, similar to cheat (Bromus tectorum) in habit, habitat, ecology

•Formerly in Spokane, Yakima, Klickitat counties; now in Kittitas, Skamania, King, Cowlitz counties

Slender false brome (Brachypodium sylvaticum) Oregon, California, Ontario

Estimates suggest infestation of at least 10,000 acres

Slender false brome (Brachypodium sylvaticum) in Oregon as of January 23, 2007

California Valley and Foothill Grassland Ecosystem…GONE!

California Valley and Foothill Grassland Ecosystem resembled PNW perennial bunchgrass ecosystems.

THEN:Dominated by Stipa pulchra; S. cernua, Danthonia californica, Festuca californica, Sitanionjubatum, Elymus glaucus, Melicacalifornica, etc.

NOW: 1)introduction of Mediterranean

annual grasses and forbs (Bromus, Hordeum, Avena, Vulpia, Briza, Brachypodium…..)

2)overgrazing 3)drought4)severe wildfire

--human-mediated disturbance climax vegetation (“disclimax”)…. permanent, incapable of returning to previous climax vegetation of perennial bunchgrass otherwise expected for regional climate and soils = novel ecosystem

Bromus, Lolium, VulpiaCalifornia

BrachypodiumCalifornia

INVASIVE GRASSES COMPROMISE ECOSYSTEM HEALTH AND INTEGRITY

Altered Key Ecosystem Processes and Services include:• nutrient cycling and carbon cycling [Aegilops triuncialis (Drenovsky and

Batten 2007)]

• sediment erosion and deposition rates (spartina; giant reed)

• disturbance intensities and frequencies [cheat (reduces fire cycle from 60–110 yrs to 3–5 yrs); medusahead; cogongrass (max temp 856º F)]

• evapotranspiration, water cycling, hydroperiods (reed canarygrass; giant reed; cogongrass)

• soil chemistry; soil biological processes (velvet grass)

• primary productivity (ryegrass)

• genetic integrity (bromes; wheatgrasses)

• resilience to disturbance (incl. biol. invasions) (bromes; cogongrass)

• habitat availability for native plants/animals/other organisms (reed canarygrass; quackgrass; cogongrass; Japanese stiltgrass; tall fescue…)

• biodiversity and associated food web interactions/characteristics

Apical Meristems

Intercalary Meristems

WHY CAN GRASSES BE SO INVASIVE??Simple modular growth form(phytomer concept: repeated building blocks containing fixed regions of cell division and origins of differentiation; basic unit of growth): node, internode, sheath, blade, and axillary bud; intercalary meristems at bases of blade, sheath and internode. Diversity derives from myriad modified versions of this basic, simple body plan.

giant reed (Arundo donax)

annual bluegrass (Poa annua)

Bermuda grass seeds (hulled)2,071,000 seeds/lb

Wind pollinated or apomictic; highly reduced (inexpensive) floral and fruit structures; efficient wind, water, and animal (human) seed

dispersal; extended seed dormancy: extraordinary capacity for sexual reproduction

hairy vetch16,000 seeds/lb

tall fescue227,000 seeds/lb

field corn3,000 seeds/lb

WHY CAN GRASSES BE SO INVASIVE??

Phleum pratensis: 1,152,000 seeds/lb vs Trifolium repens: 768,000 seeds/lb

Bromus tectorum: 400 lbs/ac vs 200-300 lbs/ac for cool season grasses

WHY CAN GRASSES BE SO INVASIVE??Simple modular growth form (phytomer concept: basic unit of

growth): node, internode, sheath, blade, and axillary bud; intercalary meristems at bases of blade, sheath and internode. Diversity from myriad modified versions of this basic body plan.

Wind pollinated or apomictic; highly reduced (inexpensive) floral and fruit structures; efficient wind, water, and animal (human) seed dispersal; extended seed dormancy (many, not all).

Generally do not produce secondary toxic compounds (glycosides, alkaloids, cyanogenics, etc) and instead avoid/tolerate grazing through morphological and anatomical mechanisms (but see allelochemicals and endophytic fungi, below).

= extraordinary capacity for vegetative growth (tillers, stolons, rhizomes, bulbils, corms, fibrous roots) and sexual reproduction….

PHOTOSYNTHETIC APPARATUS

C3: mesophyll is loosely packed; bundle sheath cells lack chloroplast.

C4: coordinated anatomical and physiological features concentrate CO2 around the C3 photosynthetic machinery through use of a solar-powered biochemical cycle; mesophyll is tightly packed and radiately arranged; bundle sheath cells with chloroplasts. PEP shuttles CO2 to bundle sheath cells. 3% of vascular plant species (C4) account for ~25% of terrestrial photosynthesis.

GRASSES ARE PRODUCTIVE

Zedler. U. WI Arboretum Leaflet 15.

Abdala, Caldas, Haridasan, Eiten (1998). (Brazil)

Mollisols: Soils formed under prairie or grassland vegetation; grasses add abundant raw organic matter to the soil, mostly by in situ root death.

More than 25% of the USA land area is covered by Mollisols, fertile soils now used predominantly for agriculture.

A Palouse-region soil profile, ID

Aboveground productivity, C:N ratios, and root:shoot ratios are higher, on average, in native grasses > non-native grasses > native forbs.

WHY CAN GRASSES BE SO INVASIVE??Pre-adapted genotypes (~11,000 species World-wide!)

Rapid evolutionary capacity (post-immigration evolution and microevolution) [Novack and Mack (2005): founder effects but high intra-population diversity from multiple introductions and novel genotypes; Longland and Ashleu 2007: evidence for local adaptation]; rapid speciation; niche specialization

Chromosomal Diversification: reduction, polyploidy, and hybridization are rampant (80% of all grasses are estimated to be polyploid); notable phenotypic plasticity within taxa (drought, cold, grazing, fire, soil fertility, soil moisture, climate change…)

Adaptation to drought and open (sunny) spaces and disturbance

Allelochemicals [Hogal and Sanford (2006): Bromus tectorum root extracts reduced growth of Hilaria jamesia by 60%; Lolium and Pinus ponderosa]

Endophytic fungi: asymptomatic fungi that occur intra- and inter-cellularly and produce secondary metabolites (alkaloids, indole–diterpenoids…)

Escape from biotic constraints

FERALCEREAL RYE(Secale cereale) Beginning in early 1960’s Compared to cultivated

varieties (~60 generatons):• shattering spikelets• delayed flowering• more tillers• shorter (smaller leaves;

thinner stems)• smaller, more seeds

Burger, J.C. and N.C. Ellstrand. 2014. Rapid evolutionary divergence of an invasive weed from its crop ancestor and evidence for local diversification. J. Systematics and Evolution 52 (6): 750–764.

ShareAlike 4.0 International (CC)

MANAGEMENT OPTIONSCultural: preventionPhysical: mowing, burning, grazing, hand-pulling

mature stands, diggingBiological: possibly some smuts/rusts or other fungi,

or bacteria; cryptogamic soil crusts; biodiversityChemical: Most useful in many situations

Lack of selectivity is still a challenge

The herbicide label is the law: read it and comply!

Technical support from companies varies widely

NON-SELECTIVE HERBICIDES FOR GRASS CONTROL

Active Ingredient

Trade Name Foliar Spot Treatment (%v/v)

Foliar Broadcast

glyphosateAromatic Amino Acid Synthesis Inhibitor (Group 2)

Roundup Pro, Accord Concentrate, Rodeo, generics

1.5% (PA, AD) 2% (MV) 4% (AD, IC) 5-10% (PhyA)

1.5-2.5 pt/ac (MV) 4-7.5 pt/ac (PA, IC) 4-5 qt/ac (AD)

imazapyrBranched-chain Amino Acid Synthesis Inhibitor (Group 9)

Arsenal, Chopper, Polaris, Habitat

Arsenal AC

2% (PhyA, IC)

1% (PhyA, IC, PA)

3-4 pt/ac (AD) 4-6 pt/ac (IC, PA) 24 oz/ac (IC) 2-3 pt/ac (PA)

hexazinone Velpar L 2 Gal/A (PhyA)

imazapic Plateau, generics 4 oz/ac (MV)

imazapic + glyphosate

Journey 10.7-16 oz/ac (MV)

Arundo donax (AD); Imperata cylindrica (IC); Microstegium (MV); Miscanthus sinensis (MS); Phragmites australis (PA); Phyllostachys aurea (PhyA). [Dr. Stephen F. Enloe, Auburn Univ, AL]

POST-EMERGENT GRAMINICIDES: “FOPS” AND “DIMS”

Active Ingredient Trade Namefenoxaprop-P Acclaim Extra

fluazifop Fusiladeclethodim Select, Envoy Plus

sethoxydim Vantage, Poast

• Many herbicides provide pre-emergence control

• A few post-emergent herbicides provide selective control of many grass species

• Select/Envoy = only post-emergent control for annual bluegrass

• Short-term vegetative control

• Very weak on large rhizomatous perennials; best on young, active

• Fail to effectively kill rhizomes

OPTIMAL TIMING OF HERBICIDES?• Treat infestations sooner than later to minimize

acreage requiring treatment

• Late summer/fall (when plants store energy belowground) is most effective window for treatment of aggressive perennials

• However, growth at that time may be too tall to treat with ground equipment without additional treatment (integrated management: mowing)

• Do not spray if targets are drought-stressed; if rainfall or heavy frost is forecast; when label says not to spray

WHY DOESN’T A SINGLE TREATMENT NORMALLY ERADICATE?

• Even short-lived seedbanks often have seed that delay emergence and escape treatment

• Leaf area of shoot growth available for herbicide uptake not adequate to get enough material belowground

• Dormant buds on rhizomes and lateral roots are not active transport sinks and escape treatment

• Environmental conditions at time of treatment influence outcome

imazapyr (Group 2)

triazines (Groups 5, 6, 7)

glyphosate (Group 9)

fops/dims

PARAQUAT-RESISTANT RYEGRASS IN GRAPES(Australian “double knock” system)

PARAQUAT OVERSPRAY DAMAGE IN SOY

• glyphosate application first (non-selective herbicide)• paraquat application two weeks later (quick-acting; contact herbicide)• developed specifically to minimize risk of developing glyphosate-resistant weeds• 20 years of use has resulted in paraquat-resistant ryegrass

Grasses are important (but often overlooked) elements of our non-native flora and will continue to be so.

Altered mechanisms of transport, increasing globalization, and continued plant importations will introduce many more invasive species to the PNW—including grasses.

Pesticide usage will increase because of expanding and newly established invasive species, resulting in increased frequency of herbicide-resistance in those target species.

Climate change will/is facilitating establishment and expansion of pathogens, pests, and invasive plants in new or previously unsuitable regions (e.g. cogon grass in SE US).

Invasive plant species will respond to climate change; some of those changes will have significant ecological, economic, and weed management implications.

Hellmann, J., J. Byers, B. Bierwagen, and J. Dukes. 2008. Five potential consequences of climate change for invasive species. Conservation Biology 22(3):534-543.

THE FUTURE?

GRASSES AS INVASIVE SPECIESClay Antieau, MS, PhC

Clayton.Antieau@seattle.gov 206-684-7413

cheatEastern Washington

reed canarygrass Washington (WA State NWCB)