How to control cabbage white butterfly and other pests.

Control of cabbage white butterfly on all cruciferious plants  (cabbage, cauliflower, broccoli, bok choy etc) can be achieved by a combination of the following methods.

• physical barriers
• cultural control
• biological control
• non toxic sprays

Physical barriers 

Before planting cruciferious seedling check each one for egg sacks or baby caterpillars (photos 1 and 2.) Placing a physical  barrier over each seedling such as the range of net pots (photo 3) obtained from a hydroponic shop  or the mesh baskets obtained from KMart  prevents access to butterflies and other creatures such as sparrows which like to eat fresh shoots.  Placing protection over the entire bed  with a frame and fine mesh  such as the one offered by this Australian company  www.veggiepatch.com.au/index.html Or use the images to devise your own design. The benefits of  mesh pots are their small size which makes for placement in mixed established beds easy and protect the plant while it is at its most vulnerable stage. The benefit of the meshed bed is lifelong protection until harvest day.

Cultural control

Intercropping checker board style with plants which are not members of the cruciferious family but have similar height will increase the chance that a cabbage moth (and cabbage root fly?) will fail to get  the required two in a row cruciferious touch downs. This failure to means the moth will not lay an egg at that time (Row, Peter 2011, the science of gardening)  

Biological control 
Make the surrounding environment around your vegetable patch attractive to natural predators of caterpillars to increases predation of caterpillars, their eggs and even the adult moth. This is done by 

• attract small insect-eating birds by providing safe nest sites and a constant supply of water. Dense plantings of native shrubs, in out-of-the-way corners will provide nesting sites; prickly shrubs give added protection from predators. Nesting boxes for birds can fulfill an urgent need created by habitat destruction.
• Insect predators of caterpillars include: assassin bugs; tachinid flies and wasps. 
• Lacewings and ladybirds eat moth eggs, tiny trichogramma wasps parasitise moth eggs; other tiny wasps like Apanteles sp. parasitise the caterpillar, the wasp larvae feed on non-essential parts of the caterpillar. When the wasp larvae are ready to pupate their exit generally finishes off the host caterpillar. Sounds gruesome but is part of nature"(quote from Frances Michaels) www.greenharvest.com.au/fact_sheets/fs_caterpillar.html

Non toxic sprays
Dipel contains Bacillus thuringiensis, or Bt for short; it is highly effective and selective against most species of caterpillars. This biological control is a bacterial stomach poison for all caterpillars, which is mixed with water and sprayed onto foliage. It must be ingested by the actively feeding caterpillar, which dies 3-5 days later. It is totally safe to beneficial insects, bees and mammals. Bt is broken down by sunlight within 4 to 7 days; so repeated applications may be necessary.
The power sprayer has a separate spray head which is important for getting to the underside of the leaves without needing to tip the tank on its side and stopping the flow of solution. This is a good design because it does not waste any solution. Dipel when mixed only lasts for 24 hour.the Eco 360 spray bottle produces a very fine spray and reaches under leaves without inverting bottle due to clever rotating nozzle design.