PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
Description of some weeds species (contd)
Dicotyledons - broadleaved weeds – .NOT ROSETTES.
FAT HEN (Chenopodium album)
Type Annual herb with an erect, angular stem
which can grow up to 1 meter.
Agricultural weed, weed of cultivated
land, can be toxic to pigs.
Leaves Upper leaves are entire and lance-shaped,
but lower leaves may be lanceolate or the
wider ones may be rhomboid. Leaf edges
usually slightly toothed. Leaves may have
a mealy appearance, particularly on the
undersurface.
Flowers Small green-white flowers occur in
hanging clusters, placed either terminally
or in the axils of the upper leaves. Each
flower has an inconspicuous floral
envelop of 5 lobes and 5 stamens. The
inflorescence has an overall mealy
appearance.
Seeds Generally black and shiny.
Roots Fibrous.
Spread By seeds.
Chenopodiaceae
Flowering stem, greenish flowers
VARIEGATED THISTLE (Silybum marianum)
Type Stout erect bushy annual or biennial
herbaceous weed, can grow to 2.5 meters.
Weed of disturbed areas, waste ground,
near creeks and rivers old stockyards, may
cause nitrate poisoning in stock. Noxious
weed in SA, Tas. & Vic. Can take over
pastures or crops. Many other thistle
species are weeds in Australia.
Leaves Strong spiny bracts surround the base of
the flower and stem.
Flowers Single and terminal on branches. Flower
heads are large (up to 60 mm across) and
showy with clusters of bright purple
florets surrounded by long stiff spiny
bracts.
Seeds Are about the size of a grain of wheat.
Roots Fibrous.
Spread By seeds via uncleaned cereal seed, feet of
humans and livestock, fleece of sheep,
wheels of vehicles, run off water.
Asteraceae
Flowering stem, purple flowers
420 Weeds - Biology, classification and identification