PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
Spread
Many control measures are designed to prevent spread of a pest either within a crop, within a
state, between states or into and out of Australia. This principle is the basis of quarantine. Computer
software packages can predict the spread of pests, diseases, weeds and beneficial organisms. They
can also define areas at risk from colonization by pests and alternative control strategies including
appropriate quarantine measures.
FLIGHT
WIND
Moth
CRAWLING
INFESTED PLANT
MATERIAL
SOIL
Cuttings
HANDS, SHOES,
CLOTHING,
VEHICLES
MOST ADULT INSECTS HAVE WINGS AND SO CAN FLY
Some insects can fly great distances, eg
– Wanderer butterfly, Australian plague locust.
– Monarch butterflies, the world’s largest migrant butterfly has a wing span of
up to 10 cm, migrates between North America and Mexico.
– Bogong and corn earworm moths migrate long distances in the eastern states
of Australia.
Some are not very strong fliers, eg
– Azalea leafminer (adult moths can only fly about 1 metre).
– Gladiolus thrips ability to spread through a crop is assisted by wind.
– Codling moths only fly about 100 metres but are also assisted by wind.
FLIGHT MAY BE ASSISTED BY WIND, AIR CURRENTS, STORMS, eg
Twospotted mites may be spread on windblown leaves.
Storms and hurricanes over-ride weather systems, eg monarch butterflies
can be blown off course, eg from North America to Britain.
Currant-lettuce aphid is thought to have been to blown by wind to Tasmania
from New Zealand.
WINGLESS ADULT INSECTS, NYMPHS AND LARVAE of many insects,
spread by crawling, eg
Weevil larvae and adults
Locust nymphs
Mite nymphs and adults
Mite
Moth and butterfly caterpillars
Caterpillar
EGGS, NYMPHS OR LARVAE, PUPAE AND ADULT INSECTS may be
transported on or in any part of a plant, eg
Bulbs - Bulb mites, bulb flies
Fruit - Fruit fly, codling moth
Nursery stock - Twospotted mite, scale insects
Packing cases - Codling moth
Cut flowers - Thrips
Seeds - Rice weevil Rice weevil larva
in seed
INSECTS WHICH MAY BE TRANSPORTED IN SOIL, eg
Root mealybugs in containers.
Black vine weevil larvae and adults in containers.
OVERSEAS PASSENGERS MAY CARRY INSECTS
On their clothing, hand baggage and other items.
ANIMALS
WATER
OTHER INSECTS, SNAILS, BIRDS, ETC
Ants may carry scales from plant to plant.
SOME ARE COMMONLY CARRIED ON WATER, eg
Springtails.
Ants
Insects and allied pests - Plant damage 37