Tuesday, November 23, 2010

Cabbage White butterfly

With  the onset of warmer weather Cabbage White butterflies are common again.

Binomial  name : Pieris rapae
Common name : Cabbage White  or Summer Snowflake  ( cute name for it!)

underneath view
top view


This butterfly is a major pest in our garden and elsewhere when trying to grow brassica type vegetables ( cabbage, broccoli, kale etc). It was accidentally introduced into Australia in about 1929 and quickly spread - a butterfly story replicated by the cane toad. It appeared in Sydney by 1941.   Appearance is basically white with a yellow tinge underneath. The male has one black spot on the wings and the female two. The eggs are laid underneath the leaves of the chosen plant singly and are about 1mm long. When they hatch the caterpillar eats large holes in  the outer leaves before moving into the middle part  with the plant being rendered useless apart for feeding to the chooks.

There are some look alikes - here is an excellent site for butterfly and insect ID that I use a lot :

http://www.brisbaneinsects.com/brisbane_whites/CabbageWhite.htm

Control is via Derris dust (Rotenone) applied regularly and after rain and Dipel ( Bacillus thuringiensis). The latter is safe in the aquaponics system whereas Derris dust is toxic to fish.  Bordeaux mixture is supposed to repel the butterfly as is growing Dill as a companion plant. I have used Derris dust and Dipel. Derris dust is easy to use as it comes in a "puff" pack.

My vegetable garden is netted to try and exclude this particular pest but they still manage to get in somehow (usually an open door) and create havoc.

I don't even try to grow brassicas in the warmer months although we still are harvesting Kale leaves regularly and still have some cabbages hanging on that will go to the chooks.

Tom

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