Basics of Turfgrass Weed Management Tim R. Murphy Crop and Soil Sciences The University of Georgia

What is a Weed? A plant out of place A plant whose virtues have yet to be discovered A flower in disguise

Is this plant a weed??? Common ragweed Poison ivy Tall fescue decreases crop yields, allergen Poison ivy skin rashes, fruit consumed by birds Tall fescue desirable turf and forage grass a weed in warm-season turfgrasses

Human beings decide which plant is a WEED!!!!

Why are weeds an annual problem? Seed and vegetative structure dormancy Prolific seed producers Spread of seed

Weed seed survival insured by: Hard seed coat (testa) Deep burial After ripening mechanisms Germination inhibitors

Weeds are prolific seed producers. Seed/Plant Broadleaf plantain 36,000 Lambsquarters >30,000 Crabgrass 53,000 Texas Panicum 23,000 Annual Bluegrass 2,000

X Weeds - Nutsedge Spring 1 ft. 43,560 Fall 3,000,000 Plants Acre 4,000,000 Tubers Acre Acre

Introduced weeds Johnsongrass Common lespedeza Crabgrass Broadleaf plantain Water-hyacinth

Factors affecting seed germination Oxygen Light Scarification Temperature Water

Why control weeds?

Control vs. Eradication -Process of limiting a weed infestation to a level that is economically or aesthetically beneficial. Eradication -Elimination of all plants and plant parts of weed species from an area.

Weeds Compete with desirable plants for sunlight, moisture and nutrients May exert allelopathic effects Reduce yields or quality of harvested product

Why do we control weeds in turfgrasses?

Turfgrass Weeds Reduce quality - leaf width, shape, color differences Reduce density - outcompete turfgrasses, can lead to erosion Decrease aesthetic value or utility of the turfgrass. - difficult to mow, disrupt uniformity of playing surfaces, safety considerations, attract insects

Develop A Plan Goals Methods Economics Alternatives Benefits

The Goal Establish and maintain a high quality, nearly weed-free turfgrass.

Integrated Weed Management Methods Preventive Cultural Biological – not available in turfgrasses Mechanical Herbicides

Preventive Methods State and Federal laws Weed-free seed, sod, sprigs Weed-free topsoil, topdressing Clean equipment Field borders

Cultural Methods Adapted turfgrasses Fertility Cultivation Water management Insect and disease control

Southeast U. S. Turfgrasses Cool-Season Warm-Season Tall Fescue Hybrid Bermudagrass Kentucky Bluegrass Common Bermudagrass Perennial Ryegrass Centipedegrass Creeping Bentgrass St. Augustinegrass Zoysiagrass Seashore Paspalum Buffalograss

Soil Fertility Effects on Weeds Low N - legumes, mosses, speedwell High P - annual bluegrass High N - common chickweed, ryegrass, annual bluegrass Low soil pH - red sorrel, broomsedge

Weeds Favored by High Soil Moisture Sedges - purple nutsedge, green kyllinga Rushes Annual bluegrass Mosses, algae Alligatorweed Pennywort

Weeds Favored by Low Soil Moisture Prostrate spurge Poorjoe Common lespedeza Prostrate knotweed

Weeds Favored in Compacted Soils Annual bluegrass Goosegrass Prostrate knotweed Common lespedeza Path rush

Weeds may indicate a nematode problem spurges Florida pusley prostrate knotweed

Mechanical Methods Mowing Hand removal

Why does mowing control tall-growing weeds? Reduces apical dominance of main stem Basal buds initiate growth Continued clipping depletes root carbohydrates Prevents weed seed formation

Why does mowing not control low-growing weeds? Primary growing point is located beneath the mower blade.

Kentucky Bluegrass

Herbicides Herbicide – a chemical used to control, suppress or kill plants. Preemergence – applied before weed seeds germinate Postemergence – applied to emerged weeds

Herbicides Turf species vary in tolerance Weed species vary in susceptibility Turfgrass species and weed identification is critical to herbicide selection!!!!

Maintain Healthy Turfgrass Manage the roots to have good shoots Soil testing is a must! Utilize cultural practices (fertility, irrigation, mowing height, etc.) to improve stress tolerance Keep mower blades sharp ! Use the best species and cultivars for your location

Identify the Weed Problem READ textbooks and periodicals Keep a diagnostic tool kit - hand lens, etc. Know the life cycle of the pest (What temp. does a specific weed seed germinate?) Is the weed the cause or effect of the problem? Confirm your diagnosis

Weed Thresholds - ?? Site - putting green, lawn, etc. People - expectations Weed - population dynamics Budget - dollars

Scouting Sites Use zig-zag pattern Make random stops

Scouting Sites Identify weeds and life cycle Record observations by area - ornamental beds - turfgrass areas * front lawn * back lawn

Scouting Sites Record density by species Low - 1 to 10% Medium - 11 to 20% High - > 20%

When to Scout? Mid-winter months - winter weeds Late-April to July - summer weeds Late summer - assess summer program Late spring - assess winter program

Developing a Weed Management Program Prevent weed introduction Properly maintain turfgrasses Identify weeds and learn life cycle Initiate control practices Preventive Cultural Mechanical Herbicides