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


What is a Weed?: 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???: Is this plant a weed??? Common ragweed 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


Slide4: Human beings decide which plant is a WEED!!!!


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


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


Slide8: 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


Slide9: Weeds - Nutsedge Spring 43,560 1 ft. Acre X 3,000,000 Plants 4,000,000 Tubers Fall Acre


Introduced weeds: Introduced weeds Johnsongrass Common lespedeza Crabgrass Broadleaf plantain Water-hyacinth


Factors affecting seed germination: Factors affecting seed germination Oxygen Light Scarification Temperature Water


Why control weeds?: Why control weeds?


Control vs. Eradication: Control vs. Eradication Control -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: Weeds Compete with desirable plants for sunlight, moisture and nutrients May exert allelopathic effects Reduce yields or quality of harvested product


Slide15: Why do we control weeds in turfgrasses?


Turfgrass Weeds: 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: Develop A Plan Goals Methods Economics Alternatives Benefits


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


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


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


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


Southeast U. S. Turfgrasses: Southeast U. S. Turfgrasses


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


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


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


Weeds may indicate a nematode problem: Weeds may indicate a nematode problem spurges Florida pusley prostrate knotweed


Mechanical Methods: Mechanical Methods Mowing Hand removal


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


Slide39: Kentucky Bluegrass


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


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


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


Scouting Sites: Scouting Sites Use zig-zag pattern Make random stops


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


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


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