Currently only found in Nelson where an eradication attempt is underway
Potential to spread throughout New Zealand
Pest of all brassica crops, and also found on nasturtiums.
Butterflies look similar to cabbage white butterfly, but are 1.5 to 2 times bigger
Eggs are small and yellow, and are laid in clusters of 30-100 on top or bottom of leaf
Caterpillars have yellow and black markings, and feed together in clusters.
Biology
Discovered in Nelson in May 2010 and currently (December 2013) the target of an eradication attempt
Adult butterflies are strong fliers, so could spread outside Nelson
They fly on warm sunny days from early spring to late autumn
Females lay eggs in batches of 30-100 on brassica leaves, and can lay up to 500 eggs in their lifetime
Caterpillars feed in groups, often stripping all the leaves from a plant before dispersing to fresh plants
Young small caterpillars are yellow with shiny black heads, then they develop black spots as they get older. Larger caterpillars are speckled grey-green and black with three yellow lines along their body and lots of pale hairs. Mature caterpillars are about 5 cm long
Mature caterpillars crawl away from the plants and spin their cocoons in vertical surfaces such as walls, fences and tree trunks.
In Nelson there are 3-4 generations per year.
Impacts
Great white butterflies feed on all brassicas
Feeding damage reduces yields and stock avoid grazing infested plants
Scouting the crop will allow detection of eggs and caterpillars.
Control
Two insect biological control agents, the parasitic wasps Cotesia glomerata and Pteromalus puparum, attack great white butterfly in Nelson and should help to reduce its populations
No insecticides are registered for use against giant white butterfly but those used against the common small white butterfly may provide control
Great white butterfly should be reported to assist the eradication program
Phone the Ministry for Primary Industries hotline 0800 80 99 66.
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