Weed ID Slides

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The first step in controlling a weed is correctidentification

C065-03

Dandelion Spiny and annual sowthistle

C062-10

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Unknown weeds cannot be properly managed

No technique controls all weed species

Not all weeds cause equal damage (thresholds)

Species respond differently to control strategies Even variants within a species (ie. herbicide resistant

biotypes)

Weed Research and Info Centerhttp://wric.ucdavis.edu

Online weed ID tool

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A number ofweed booksare available

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Several available.

I use a set by XID Services-UC Davis-WSSA-WSWS

- others

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A few online(FREE) resourcesare available

UC Davis Weed Research

and Information Centerwww.wric.ucdavis.edu

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UC Integrated Pest Management Program

http://ipm.ucdavis.edu/PMG/menu.weeds.html

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Are they terrestrialor aquatic?

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Monocot seedlings have only oneseed leaf (cotyledon) and the leaveshave parallel venation

Grasses- with or without ligules andauricles. The leaf sheaths are split andwrapped around the stem

Sedges- no ligules or auricles. The leafsheaths is continuous around the stem.The stems may be triangular in crosssection

Dicot seedlings have two seed leaves(cotyledons) and the leaves havenetted venation

Parallel venation 

Netted venation 

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Barnyardgrass Yellow nutsedge

Grass Sedge  

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Black nightshade Annual morningglory

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What is theirlifecycyle?

Are they annual,biennial, or perennial?

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Summer annuals germinate in springand summer, produce flower and fruit

in mid- to late summer and die in thefall

Winter annuals germinate in the falland winter, flower and fruit in mid- to

late spring and die in the spring andsummer

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Filaree

Winter annual 

Purslane

Summer annual 

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Biennials live for two growing seasons.

Seeds germinate and overwinter as a

basal rosette with a thick storage root. The stems flower and produce seed in

the summer of the second season anddie in the fall.

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Common burdock Wild carrot

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Perennials live for more than twoyears and they may be:

Simple herbaceous- reproduce only fromseeds but if the plant is injured or cut,each piece can regenerate into a new plant

Creeping herbaceous- over-winter and

produce new vegetative structures such asrhizomes, tubers, stolons, bulbs etc.

Woody plants- have woody stems

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Dandelion

Simple herbaceous 

Johnsongrass

Creeping herbaceous 

Poison oak

Woody pl ant 

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Look at leaves

Netted or parallel veins?

Leaf shape and margin texture Presence of hairs or other structures

Look at flowers, and fruit/seeds,if present

Look at roots

Tap root, fibrous roots, rhizomes,stolons, tubers, etc

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Look forcotyledons and

subsequent leaves– their shape,texture etc can giveyou and idea

True leaf  Cotyledon

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Look for auricles andligules, shape of the

sheath, hairiness of thesheath, seed heads

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Auricle: an

appendage that

grows from theedge of the collar

and may wrap

around the stem.

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Ligule: a structure

that grows from

the collar area onthe inner side of 

the leaf. Ligule

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