PEST

NAME
Cabbage White Butterfly
Pieris rapae

ORDER
Lepidoptera

FAMILY
Pieridae

Description of the Pest
There is a male and female adult butterfly, both are grey-white but the female has two black spots on the forewings and the male has one. The wingspan is up to 50mm (2in) wide and both sexes have a single black spot on the hindwings.
The small larvae is up to 30mm (1Ľin) long with a velvety, pail green appearance and as it matures it also displays a faint yellow stripe (little yellow spots) along its back and on both sides.

Male Adult butterfly one spot on forewing

Life cycle
This insect has a Holometabolouslife cycle, i.e. it has alarvaland a pupal stage.
This insect is a serious pest problem throughout the world and is difficult to see as they camouflage well with the plant.

Distribution of the Pest
World wide and Australia wide

     
Resting adults

Period of Activity
The caterpillars are most active during autumn or spring but in warm regions they can be found throughout the year. There are two to several generations each year. The larva overwinters in cocoons that are on the host plant or near by. The adult moth can fly up to six kilometres to find a host.

Damage Caused
Most of the feeding occurs during night and the larvae rest in daylight. The young larvae with chewing mouthparts, feed on the under surfaces of the leaf and mature larvae may be seen eating large irregular holes. Dark green pellets of excrement may be seen around infested plants.
The insect secures itself with silk before feeding.
The caterpillars chew large holes in leaves, seriously interfering with the plants growth and the adults feed on the nectar of the flowers with its siphoning mouth parts. Commercial crops may be rendered unsuitable for human consumption by the actions of this lava.

Susceptible Plants
Many plants are attacked, cultivated leafy vegetables such as cabbages, cauliflowers, broccoli and radishes. Weeds and other ornamentals such as Mathiola incana ,Cheiranthus cheiri andCleome species are also attacked. Younger plants are more susceptible to attack. The insect uses glycosides found in members of the Brassicaceae family as a chemical defense mechanism, the poison deters predators.

Control

Cultural Control
In small infestations caterpillars may be removed by hand.
Keep the crops weed free and remove heavily infested plants.
Inter row planting with flowering companion plants (carrot family, Apiaceae <en.wikipedia.org/wiki/Apiaceae>) may reduce attack by attracting predators and parasites to the area.
Plants including seedlings may also be covered by a protective net
A maturing Brassica plant that is flowering may also be used as a decoy for seedlings as the adult lays eggs where it feeds. This plant can be later removed.

BiologicalControl
The lava is attacked by; parasitic wasps at different stages in their life cycle.
Pteromalus puparum parasitises the pupa. Apanteles glomeratus and A. rubecula parasitises the larva.
Ants are predators of the larva; unfortunately this includes the slower moving parasitise larva.
Bacillus thuringiensis(Bt) a bacterial disease may be used
In some commercial Brassicaceae crops Bt has been included in the plant which avoids the use of sprays.

Chemical Control
Chemical control may be controlled with stomach or contact insecticides, to the underside of the leaves.

Note
It is your responsibility by law to read & follow the directions on the label of any pesticide

Monitoring
Beat the plants on to a stiff white cardboard to collect the larvae on a weekly basis

Amendments by B. Sonsie Dip Hort Sc Burnley