Video / Photo Dictionary

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Abaxial: The lower side of the leaf blade located away from the axis.
Acropetal penetrant: a partially systemic fungicide that only moves upward within the plant’s xylem from its point of uptake.
Adaxial: The upper side of the leaf blade located on the same side as the axis.
Aerification: The practice of improving the movement of air, water, and nutrients into the soil by making holes or slits in it. Machines are commonly used to remove plugs of soil.
Algae: Primitive cyanobacteria that contain chlorophyll, thrive in wet soils, and form a scum that yields anaerobic soil conditions.
Anthracnose: A major disease of annual bluegrass putting greens that is caused by the fungal pathogen Colletotrichum cereale.
Apical meristem:
Terminal growing point.
Axillary bud: Vegetative bud growth arising from the junction of leaf and stem.

Bacterial wilt: A difficult to control disease of annual bluegrass putting greens that is caused by the only bacterial pathogen found in turf. The disease is identified by the presence of streaming bacteria from the vascular cylinder of infected plants.
Black layer:
A physical soil condition marked by lack of oxygen, which leads to poor root development and health.
The expanded or flattened part of a grass leaf located above the sheath.
Blend: A combination of two or more cultivars of the same turfgrass species.
Brown Patch: A common foliar disease of turf which often occurs during the heat of the summer months.
Reproductive structures that are capable of regenerating new, independent plants.
Bunch type growth: Plant development by intravaginal tillering at or near the soil surface without production of rhizomes or stolons.

Chlorosis: The yellowing of normally green plant tissue because of the lack of chlorophyll.
Collar: Light colored band at the junction of the blade and sheath on the abaxial side of the leaf.
Contact fungicide: A chemical that reduces disease by forming a protective barrier on the outside of a plant.
Cool season grass: Species adapted to more favorable growth during cool portions (60 to 75F) of the growing season; may become dormant or injured during hot weather.
Coring: A method of turf cultivation by which soil cores are removed using hollow tines or spoons (see aerification).
Crown: A highly compressed stem located at the base of a vegetative aerial shoot.
Cultivar: An assemblage of cultivated plants distinguished by any characters (morphological, physiological, cytological, and the like) that when reproduced sexually or asexually retain their distinguishing features.
Cultivation: Applied to turf, cultivation refers to working of the soil and/or thatch without destruction of the turf; for example, coring, slicing, spiking, or other means.
Cutworms: Cutworms can be destructive insects, particularly on golf courses and other highly maintained turf areas.

Damping: off: Decay of seeds in the soil or young seedlings before or after emergence.  Most evident in young seedlings that suddenly wilt, topple over, and die from rot at the stem base.
Denitrification: Biological reduction of nitrate or nitrite to gaseous N.
Dessication: Loss of moisture from a plant because of hot, dry weather or chemicals.
Disease triangle: A concept describing the simultaneous occurrence of a virulent pathogen, a susceptible host, and a favorable environment that are required for a disease to develop.
Dissemination: In relation to plant disease, spread of inoculum.
DMI: Demethylation-inhibiting fungicides.  A group of fungicides that prevent demethylation processes from occurring as fungi try to synthesize ergosterol from squaline for cell membrane formation.  (e.g., fenarimol, propiconazole, triademefon).

Endophyte: A fungus living within a plant in a symbiotic relationship that may protect the plant from select pests.
The part of a seed that contains stored food.
Evapotranspiration: Total loss of moisture through the processes of evaporation and transpiration.
Exudate: Liquid excreted or discharged from diseased tissues, from roots and leaves, or by fungi.

Facultative parasite: Organism that is normally saprophytic but is capable of being parasitic.
Facultative saprophyte: Organism that is normally parasitic but is capable of being saprophytic.
Fertigation: The injection of small amounts of liquid fertilizer into the irrigation stream on a regular basis.
Field capacity: Tthe amount of moisture remaining in the soil after gravitational moisture has drained.
Foliar burn: Injury to shoot tissue caused by dehydration due to contact with high concentrations of chemicals such as fertilizers or pesticides.
Foliar-feeding: Practice of spraying light rates (0.1 to 0.125 lb N/1000 sq ft) of water soluble fertilizer on 7 to 14 day intervals during the summer months.
Footprinting-frost: Discolored foot-shaped areas of dead leaf tissue created by walking on live frosted turfgrass leaves.
Footprinting-wilt: Temporary foot: shaped impressions left on a turf because the flaccid leaves of grass plants suffering incipient wilt or wilt have insufficient turgor to spring back after treading.
Fruiting body: A fungal structure in which spores are produced.
Fumigant: A gas or volatile substance used to kill or inhibit the growth of microorganisms or other pests.
Fungicide: Chemical or physical agent that kills or inhibits the growth of fungi.
Fungistat: Chemical agent that inhibits fungal growth or sporulation but does not kill fungi.
Fungus: An organism composed of hyphae and lacking chlorophyll, which is saphrophytic and/or parasitic.

Germ tube: Hypha resulting from an outgrowth of the spore wall and cytoplasm after germination.
Grain: The horizontal orientation of grass stems and leaves in one direction.

Humus: The well-decomposed, more or less stable portion of soil organic matter content.
Hybrid: Product of a cross between individuals of unlike genetic constitution.
Hypha (pl. hyphae): Tubular filament of a fungal thallus or mycelium; the basic structural unit of a fungus.

Infest: To attack as a pest (used especially of insects and nematodes); to contaminate, as with microorganisms; to be present in large numbers.
Inflorescence: The flowering part of a plant where the seed develops.
Inoculum: Parts (spores, mycelium, nematodes, virus particles) of a pathogen that are able to cause disease.
Internode: Portion of the stem between two successive nodes.

Japanese beetle : A common insect that can cause significant damage to both broadleaf plants (as adults) and established stands of turf (as grubs).


Ligule: An upright, membraneous or hairy projection located where the leaf sheath and blade join.
Localized dry spot: Dry spot of sod amid normal, moist turf that resists rewetting by normal irrigation and rainfall; associated with a number of factors, including thatch, fungal activity, shallow soil over buried material, or elevated sites in the terrain.

Mat: A tightly intermingled layer composed of living and partially decomposed stem and root material and soil from topdressing or other sources that develops between the zone of green vegetation and the soil surface.
Meristem: Undifferentiated tissue with cells capable of division at the tip of a stem or root (apical) or at the base of a leaf (intercalary).
Mixture: A combination of two or more species.
Moss: Small plants which lack a vascular system and thrive in moist and shaded environments.
Mulch: Any nonliving material that forms a covering on the soil surface.
Mycelium: Mass of hyphae constituting the body of the fungus.

Necrosis: Death of cells or tissue, usually accompanied by blackening or browning.
Nitrification: Formation of nitrates and nitrites from ammonia by soil microorganisms.
Node: The joint of a stem; the region of attachment of leaves to a stem.

Obligate parasite: Organism that can grow only as a parasite in association with its host plant and cannot be grown in artificial culture media.
Oomycetes: A class of fungus-like organisms, typically with nonseptate mycelium, asexual sporangia and zoospores, and sexual oospores.
Oospore: Thick-walled, sexually derived resiting spore of fungus-like organisms in the class Oomycetes.
Overseed: Seeding into an existing stand of turf.

Patch: In grasses, a distinctly delimited, somewhat circular area in which most or all plants are affected by disease.
Pathogen: A disease-producing organism or agent.
Pesticide: Chemical agent used to control pests.
pH: A numerical measure of the acidity or hydrogen ion activity of a system.
Phenotype: The physical properties of an organism produced by the interaction of its genotype with the environment.
Phloem: The principal food-conducting elements of vascular plants.
Photoperiod: Period of a plant’s daily exposure to light.
Photosynthate: A product of photosynthesis.
Photosynthesis: Manufacture of carbohydrates from carbon dioxide and water in the presence of chlorophyll, using light energy and releasing oxygen.
Phytotoxic: Harmful to plants.
Primary inoculum: Inoculum (usually from an overwintering source) that initiates disease in the field, as opposed to inoculum that spreads disease during the season.


Recuperative capacity: The capacity of turfgrasses to recover from injury; usually through vegetative growth from axillary buds.
Reel mower: A mower that has a rotating reel which cuts against a statioinary bedknife.
Residual: The property of a pesticide for persisting after application in amounts sufficient to kill pests.
Resiliency: The capacity of the turf to spring back when balls, shoes, or other objects strike the surface, thus providing a cushioning effect.
Resistant: Possessing properties that prevent or impede disease development.
Respiration: Series of chemical reactions that make energy available through oxidation of carbohydrates and fat.
Resting spore: Spore, usually thick-walled, that may remain alive in a dormant state for months or years, later germinating and capable of causing infection.
Rhizome: An underground elongated stem (or shoot) with scale leaves and adventitious roots arising from the nodes.

Sanitation: Destruction or removal of infected and infested plants or plant parts; decontamination of tools, equipment, containers, work space, hands, etc.
Saprophyte: Organism that obtains nourishment from nonliving organic matter.
Scald: A necrotic condition in which tissue is usually bleached and has the appearance of having been exposed to high temperatures.
Scalp: To remove an excessive quantity of functioning green leaves at any one mowing; results in a stubbly brown appearance caused by exposing crowns, stolons, dead leaves, or even bare soil.
Sheath: The tubular basal portion of the leaf that encloses the stem.
Shoot density: The relative number of shoots per unit area.
Sign: An indication of disease from direct observation of a pathogen or its parts on a host plant.
Soil drench: Application of a solution or suspension of a chemical to the soil, especially a pesticide to control soilborne pathogens.
Spore: A reproductive structure of fungi and some other organisms, containing one or more cells; a bacterial cell modified to survive an adverse environment.
Spot: A symptom of disease characterized by a limited necrotic area, as on leaves, flowers, and stems.
Stolon: An elongated stem (or shoot) that grows along the surface of the ground and from which leaves and adventitious roots develop at the nodes.
Stomates: Openings in the epidermis of leaves and stems that function in the exchange of gases between the atmosphere and the plant.
Syringe: To spray turf with small amounts of water to (a) dissipate accumulated energy in the leaves by evaporating free water rather than by transpiring plant water; (b) prevent or correct a leaf water deficit, particularly wilt; or (c) remove dew, frost, and exudates.

Thatch: The accumulation of undecomposed or partially decomposed organic material located above the soil surface. The thatch layer is primarily composed of dead and living root and stem tissue.
Tiller: A lateral shoot, usually erect, that develops intravaginally from axillary buds.


Verdure: The layer of aboveground green living plant tissue remaining after mowing.
Vertical mowing:
Cutting slices in the turf with a machine that has blades mounted on a vertically rotating shaft.

Weed: A plant growing where it is not wanted.
Wet-wilt: A situation where the plant cannot uptake enough water to allow transpiration despite the presence of adequate soil moisture.






Christians, Nick. Fundamentals of Turfgrass Management. 2nd ed. Hoboken, NJ: John Wiley & Sons, 2004.

Dernoeden, P.H. Creeping bentgrass management: summer stresses, weeds, and selected maladies. Hoboken, NJ: John Wiley & Sons, 2002.

Emmons, R.D. Turfgrass Science and Management. Delmar Publishers.

Smiley, Richard W., Dernoeden, Peter H., and Clarke, Bruce B. Compendium of Turfgrass Diseases. 3rd ed. St. Paul, MN: American Phytopathological Society, 2005.

Turgeon, Alfred J. Turfgrass Management. 7th ed. Upper Saddle River, NJ: Pearson Education, 2005.

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