Weeds
Chapter 7
Section VII
of the
Pest Bear & AffiliatesService Personnel Development Program
2005
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Introduction
Weed control is probably the most challenging part of pest control. It requires an intimate knowledge of the plants and the selection of a control process may become extremely difficult due to the variety of desired plants which may be in the vicinity.
Before attempting weed control, it is paramount to your success to properly identify the target weed. Always remember that a weed is simply “a plant out of phase with man” and one persons weed may be a desired plant to some one else.
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Dandelion
Yellow Woodsorrel
White Clover
Pennywort
Nutsedge
IntroductionIn order to develop the identification of weeds, we
have selected groups of plants which will be presented in several weed identification groups.
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Bull Thistle
Timothy
Foxtail
Barnyardgrass
Goosegrass
Crabgrass
Quackgrass
Canada Thistle
Ground Ivy
Spurge
Dandelion (Taraxacum Officinale
•Perennial with long tap root
•reproduces by seed
•Stems short arising from a rosette bearing oblong, lobed, narrow leaves
•Large yellow flowers mature in round puffballs full of seeds
•Seed distributed by wind for miles
•Mostly germinates during late summer
•controlled by mechanical and chemical means
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Yellow Woodsorrel (Oxalis Stricta)
•Annual to short lived perennial
•Upright, with single tap root
•Spreads by seed
•leaves of three, heart shaped, pale green and bitter to taste due to the presence of oxalic acid
•Bright yellow flowers have five petals
•Prolific seed producer
•Pods will scatter seed for several feet when touched
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White Clover (Trifolium repens)
•Perennial legume
•More common in nitrogen deficient lawns and in years with excessive moisture
•Leaves have three leaflets with white water marks
•Creeping stems are very aggressive and root at the nodes
•White flowers sometimes seen with a tinge of pink are a favorite of bees
•Seeds may live in soil for 20 years
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Pennywort (Hydrocotvie sp.)Also called Dollar Weed
•A Perennial weed
•Grows from rhizomes, tubers and seed
•Erect leaves with scalloped margins on a long petiole in the center of an umbrella like leaf
•Found in moist to wet sites
•Most common in Transition Zone in the South
•Control of moisture is critical to regular maintenance program
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Nutsedge (Cyperus sp)
•Also known as nutgrass, but is not a grass
•Perennial , reproduces by seed and nut like tubers on roots
•Stems are erect and triangular
•Leaves 3-ranked, narrow, grass-like basal
•Seed on unmowed plants arranged in narrow spiklets
•Yellow nutsedge has single fleshy tubers on ends of roots
•Purple nutsedge has string of tubers on wiry rhizomes
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Bull Thistle (Cirsium vulgare)
•A biennial which grows into a rosette
•Has large, fleshy, coarsely-toothed spiny leaves
•In the second year, will have a woody, flowering stalk
•Produces a few, rose-purple blossoms
•Produces less flowers than Canada Thistle
•All flowers are fertile
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Timothy (Phelum pratense)
•A tufted biennial
•Tends to persist as a perennial
•Sharply pointed leaves roll into a bud
•Ligule is distinctly notched
•The bulbous crown area of the base of the stem resembles an onion
•A reddish color at the base
•There is no selective means of control
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Foxtail (Setaria sp.)
•An annual grass that germinates about the same time as crabgrass
•found in sun and partial shade
•Erect round stem with leaves rolled into a bud
•Prominent ligule, blades flat with long sparse hairs
•Sheaths may be reddish at the base
•Seed head is bristly and spike-like
•Green, yellow, bristly and knotroot foxtail are all in same genus
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Barnyardgrass (Echinochloa crusgalli)
•A coarse bladed annual grass
•Leaves roll into a blade and sheaths are flat and compressed
•Sheaths are red to purple at the base
•There is no ligule
•A panicle seed head with barbed spikelets and awns
•Unmowed will grow to 2 feet or more
•Common in open areas germinates late in the season
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Goosegrass ( Eleusine indica)
•An annual grass with rosette of flat stems
•Usually silvery at the center
•Leaves are folded with stems overlapping
•A membranous ligule with sparse hair on the collar
•Seed heads form 2-10 finger- like spikes, broader than crabgrass
•Germinates later than crabgrass
•Persists under close mowing, even on golf courses
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Crabgrass (Digitaria sp.)•True annuals
•Germinates from seed at 55-60º for five consecutive nights
•Yellow-green leaves rolled into a bud with hairy edges, coarse texture and broad collar
•Blade flat with sharp point
•Seed head with 3-10 fingers
•May appear purple or tan
•Declines after seeding with shorter days
•Eliminated by frost
•Found throughout the US and mostly in sunny areas
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Quackgrass (Agopyron repens)•Blue-green rough bladed perennial
•Reproduces by seeds and aggressive rhizomes
•Erect stems
•Leaves rolled into a bud and have a hairy sheath
•A membranous ligule with very prominent clasping auricles
•Has a spiked seed head which resembles perennial ryegrass
•Spreads throughout the lawn from ornamental beds
•Very difficult to control
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Canada Thistle (Cirsium arvense)•Tough perennial
•Grows from seed and aggressive rhizomes
•Oblong leaves are lobed with spiny toothed margins
•Small lavender to rose colored flowers are found on 1-5 foot stems
•Invades lawns through ornamental beds
•Plants from rhizomes tend to be singular and scattered in patches
•Very difficult to control
•Requires a persistent control program
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Ground Ivy (Glecoma hederacea)
•Perennial plant
•Member of the mint family and has square stem and distinct odor
•Reproduces by seeds and creeping stems which root at the nodes
•Forms dense patches in sun or shade
•Has opposite leaves with scalloped edges
•Leaves are rough on the upper side
•Flowers are trumpet shaped and purple in color
•Flowers in the spring
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Spurge (Euphorbia maculata)•A summer annual
•Germinates from seed when the soil is 55ºF and continues all summer
•Small, oval, opposite leaves
•Vary from green to red with a brown blotch on upper surface
•Reddish, low growing stems that fan out from a tap root
•Form dense mats of vegetation
•Milky sap is sticky
•Each plant may produce several thousand seed
•Plants mature in matter of days in hot weather
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It is Important to Know
•If the plant is an annual or perennial
•If the plant reproduces by seed, tuber, or rhizome
•What the plant stem and leaves look like
•What the Flower, if any, looks like
•How does the plant dissimulate
•When is the primary germination period
•Can the plant be controlled mechanically or with chemicals
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