PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
CLASSIFYING
WEEDS
HABITAT. eg
Terrestrial, eg lantana
Parasitic, eg broomrape
Aquatics weeds, eg salvinia
Riparian (creeks, rivers), eg willow
Turf, pasture, eg oxalis
Agricultural weeds, eg wild oats
Cultivated land, eg barnyard grass
Garden weeds, eg chickweed
Stockyards, eg fat hen
Waste places, eg wireweed
LAND-USE MANAGEMENT SYSTEMS.
In nine land management systems associated with cropping in Australia, weeds were
ranked as the worst problem by over 90% of farmers. Annual ryegrass, wild oats and
wild radish rated highest (Sindel 2000).
Crop weeds, eg annual ryegrass Lawns and sports turf, eg paspalum
Pasture weeds, eg serrated tussock Plantation forests, eg lantana
Environmental, eg bitou bush Australian rangelands, eg rubber vine
Vegetables, eg barnyard grass Aquatics, eg water hyacinth
Tree crops, viticulture, eg cape weed
Annual weeds are
mostly opportunists that
germinate when the soil
is at least partially bared
through seasonal
conditions following
overgrazing, mowing,
cultivation, burning
or other site disturbance.
Perennial weeds are
difficult to control due
to their underground
vegetative structures, eg
rhizomes, bulbs, etc.
Most roots can grow as
deep as 45 cm below
ground sometimes as
deep as 3-4 meters
(see inside back cover).
In their native country
these weeds are kept in
check by climate, soils,
associated vegetation,
insects and diseases
ANNUALS, BIENNIALS, PERENNIALS. Life history
Annuals. Plants which flower, produce seeds and die in 1 year or less, eg
chickweed. Control should aim to prevent further seeding. Roots are usually shallow
and plants easily hoed, hand pulled or controlled with herbicide.
– Seed production commences after a short period of vegetative growth, with
flowering and seed production high in good seasons, but low in poor seasons.
– Seed persistence, long period of seed survival, size of the seed bank.
– Germination, seedling growth and establishment is rapid.
Biennials. Plants which live for 2 years/seasons may produce seeds within
12 months or in the 2 nd year. Not many weeds are true biennials; Paterson's curse is
sometimes biennial. Control in the 1 st year of a biennial plant’s life before it sets seed.
Perennials live for 3 years or more, may be short or long lived, they may be
herbaceous or woody species. Plants have rhizomes, corms, lignotubers, deep roots or
similar structures and so can regrow year after year. Most reproduce also by seed.
Control aims to deplete root reserves so that no new shoots can develop. For some,
cultivation should be avoided, as this can lead to further spread. Those with shallow
roots and not prone to sucker can be dug out. Systemic herbicide applications may be
required for control of deep roots, bulbs and other underground structures.
GROWTH HABIT, TISSUE STRUCTURE, HERBACEOUS, WOODY.
Growth habit, eg
– Grasses, herbs
– Trees and shrubs
– Climbers, creepers, scramblers, vines
Tissue structure, eg
– Rosette, eg dandelion, capeweed
– Stolons, eg couch grass
– Rhizomes, eg Mullumbimby couch
– Suckers, eg poplar
– Tubers, eg nutgrass
– Corms, eg onion grass (Guildford grass)
– Bulbs, eg wild onion
Herbaceous, woody, eg
– Herbaceous weeds, eg ryegrass
– Woody weeds, eg some species of willow, hawthorn, camphor laurel
INTRODUCED AND INDIGENOUS WEEDS.
Introduced (alien, exotic) weeds are plants growing in an area where they are
not native, eg those native to a region outside Australia. The great majority of weeds in
Australia are introduced plants, some of which are also desirable crop, pasture, forestry
and ornamental plants.
– Pioneer species quickly colonize disturbed and denuded land, so many are
weeds of cultivation, pastures, roadsides, waste places, bush land and park land.
– Casuals or casual aliens are those that only survive for a short time because they
cannot establish self-sustaining populations and only persist by new introductions.
Australian native plants are plants that have evolved in Australia or migrated by
long distance dispersal before European settlement.
– Indigenous plants are found naturally in a particular area in Australia, but not
in Australia generally, eg sweet pittosporum is indigenous to east Victoria.
– Indigenous weeds. Many plants native to Australia can themselves become
environmental weeds within Australia, eg sweet pittosporum from east Victoria is
an environmental weed in SA and NSW and coastal Victoria. Golden wreath
wattle (Acacia saligna) from WA is now found along the NSW coast.
Weeds - Biology, classification and identification 413