HPIPM:Annual bluegrass

Taxonomy

Domain	Eukarya
Kingdom	Plantae
Phylum	Magnoliophyta
Class	Magnoliopsida
Superorder	Lilianae
Order	Poales
Family	Poaceae
Genus	Poa

Scientific Name

Poa annua

Common Name

annual bluegrass

Annual bluegrass (Poa annua)

Compiled by Sandra Frost, University of Wyoming, Northwest Area Extension, Big Horn Basin Area Crop Systems Educator

and Marjolein Schat, Montana State University from the following sources:

http://www.weedalert.com/weed_pages/wa_annual_bluegrass.htm

http://www.ppws.vt.edu/scott/weed_id/poaan.htm

http://ohioline.osu.edu/srt-fact/0003.html

http://www.msuturfweeds.net/details/_/annual_bluegrass_47/

http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7464.html

Pacific Northwest Weed Management Handbook at http://weeds.ippc.orst.edu/pnw/weeds http://oregonstate.edu/weeds/

Identification and Life Cycle

Annual bluegrass (Poa annua) is a low growing cool-season grass in the family Poaceae. Annual bluegrass leaf blade tips are prow-shaped, and leaves tend to be crinkled at the midsection. The ligule is membranous and rounded. Mature plants grow in dense tufts, 3 to 12 inches tall with roots at the lower nodes. The inflorescence (flowering structure) is a terminal spreading panicle that varies between 1 and 4 inches in length. The root system is fairly shallow and weak, requiring moisture from rain or frequent irrigation.

Habitats

Annual bluegrass grows well in moist areas in full sun.

Impacts

Annual bluegrass is a major weed in turf where it provides a weak sod that leads to poor footing in athletic fields and golf courses. Annual bluegrass is also weedy in alfalfa, grass seed, small grain, and potato.

Biology and Ecology

Annual bluegrass seeds begin to germinate in late summer or fall as soil temperatures drop below 70°F. Seedlings mature in the fall and overwinter in a vegetative state. Seed is produced in late spring and early summer. Individual plants can produce over 350 seeds. Seeds can remain dormant in the soil for several years before germinating. Plants can flower at six weeks old and viable seed can be produced a few days after pollination, allowing plants to produce seed even when frequently mowed.

Biological Control

A bacterium is being considered for registration as a bioherbicide. The bacterium, Xanthomonas campestris pv. Poae, infects and suppresses the growth of annual bluegrass without affecting desirable turfgrass species. It infects Poa plants through wounds in the stem and leaf tissues and multiplies in the vascular system, causing wilting and death of the plants.

Mechanical and Cultural Control

Close mowing encourages seeding.

Chemical Control

There are reports of annual bluegrass resistance to a number of herbicide families including photosystem II inhibitors (Alabama, North Carolina, Oregon, Mississippi, and Virginia), ureas and amides (Oregon), thiocarbamates (Oregon), and dinitroanilines (North Carolina). For a complete list of reports of herbicide resistance in annual bluegrass globally please see http://www.weedscience.org/Summary/USpeciesCountry.asp?lstWeedID=130&FmCommonName=Go

For herbicide recommendations for specific grain rotations and weeds in Montana, please see the MSU Herbicide Chooser Tool.

Examples of herbicides that can be used to manage annual bluegrass

Consult herbicide labels for additional rate, application, and safety information. Additional herbicide information can be found at http://www.greenbook.net.

Herbicide Active Ingredient trade name	Mode of Action	Product per Acre	Application Time or Growth Stage
Alfalfa
Pendamethalin	Microtubule assembly inhibition
*Prowl H2O		4 pints	Apply to established seed alfalfa before alfalfa exceeds 12 inches in height.
Imazamox	Inhibition of acetolacetate synthase ALS (acetohydroxyacid synthase AHAS)
*Raptor		6 ounces	In Alfalfa apply before annual blue grass reaches 3 inches in height.
Wheat
Glyphosate	Inhibition of EPSP synthase
*Roundup Ultra		9.5 ounces	Apply before bluegrass reaches 10 inches in height, before planting or emergence of the crop.
Grass Grown for Seed
Glyphosate	Inhibition of EPSP synthase
*Roundup Original max		11 ounces	Apply before bluegrass reaches 10 inches in height, before planting or emergence of the crop.

The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.

References

For more information and images please visit IPM Bugwood. http://www.ipmimages.org/search/action.cfm?q=Poa%20annua