PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
SPREAD
(dispersal)
Weeds
generally
spread very
efficiently and
are spreading
faster across
Australia than
they can be
contained
H 2 O
Weeds spread very efficiently by:
RHIZOMES, STOLONS, TUBERS, SUCKERS (page 426)
Climbing weeds, eg bridal creeper, will climb over adjacent plants.
WIND AND AIR CURRENTS
Some weed seeds are very light and have attachments of silky hairs, parachute-like
structure or downy coverings which may travel for many miles on air currents. Wind
can blow seeds. Pampas grass can produce 100,000 seeds per plume which can be
carried more than 39 km to invade the bush.
EXPLOSIVE MECHANISMS
Seed capsules of oxalis and flickweed (Cardamine hirsutus)
open explosively and spread to adjacent pots.
WATER
Some weeds, eg Noogoora burr, are adapted to float on water or to be moved by the
force of running water. Generally seeds, fruit, bulbils and other plant parts can wash
down drains into waterways where they grow and spread. Irrigation water can be a
source of weed entry. Floods spread seed of Mimosa pigra and willow parts.
ANIMALS
In manure. Some weed seeds may pass undigested through animals, eg birds, feral
pigs, possums, stock, foxes, so that their manure may carry viable weed seeds some
weeds. Manure deliveries may contain weed seeds, eg nettle seed in sheep manure.
Birds eat fruits and seeds of weeds, eg blackberry, cotoneaster, lantana, mistletoe,
privet, spreading seed through bush where the seed germinates. The seeds of
cotoneaster can be carried for many kilometers in the digestive tract of animals.
Flying foxes eat fruit and seed and carry it to nearby bushland.
Adherence to animals. Seeds with burrs may attach to wool, fur, feathers and
feet of animals and may even penetrate hides, eg corkscrew grass (Aristida sp.).
Pets carry seeds from garden to bush land on fur.
HUMANS.
Quarantine. Up to 70% of weeds were intentionally introduced to Australia in
the early days of settlement for crops, pasture or as ornamental plants. Seeds and
other plants have been brought in unintentionally in agricultural products aboard
ships and air craft, importing contaminated seed from overseas. Many plants
previously used as crops or ornamentals are today's weeds.
Crop seed unintentionally sown after harvesting from weed-infested crops.
Sale of invasive or potentially invasive plants.
Nursery containers may contain weeds, weed seeds or stolons of weeds, eg
creeping oxalis, flick weed. Weeds spread to gardens, parkland, etc.
Movement of contaminated fodder hay, chaff, or mulch, agricultural
produce can result in weed outbreaks in new areas, eg dodder, thistles.
Seeds with burrs which attach to clothing, socks, trouser legs, shoes.
Garden plants which have spread from where they were originally planted in
gardens and urban parks, eg Scotch broom, lantana, hawthorn, gorse.
Dumping of garden waste, eg rhizomes, bulbs, cuttings and prunings which may
produce new plants, over back fences or into bushland or forests. Emptying
aquarium plants into drains, waterways, eg water hyacinth, salvinia, equisetum.
Direct invasion from neighbouring properties, eg ivy may creep
vegetatively from gardens into parkland.
Moving soil and plant material through the landscape, eg soil deliveries, soil
and gravel removed from river banks, etc.
Machinery and vehicles. Seeds, bulbs, and other plant parts are carried on
slashers, graders, mowers, vehicle tyres, tools, boats, trailers, camping equipment.
Unfiltered or recycled water, recycled potting mix.
Fortuitously, eg vehicles parked under trees which are seeding, eg alder trees.
Weeds - Biology, classification and identification 427