Ladybirds

Ladybirds, except for the leaf-eating 26 or 28 spot ladybirds, are an asset to any garden. Both adults and larvae consume a considerable quantity of pests such as aphids and scale, and one type of ladybird feeds on fungus.
Most people know what adult ladybirds look like but ladybird larvae are strange looking creatures and many people confuse them with garden pests. As a result many of these hardworking pest predators are killed by pesticides, including organic sprays, and a decline in ladybird numbers is always followed by a pest outbreak. A common victim is the larvae of the Cottonycushion Scale ladybird which disguises it self so well, it is often mistaken for scale. A Brisbane web site has an excellent range of photos of ladybirds and their larvae. Check before you spray so that ladybirds won’t become an endangered species.
http://www.brisbaneinsects.com/brisbane_ladybirds/index.html

The cabbage family

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This family, called the Brassicas, tend to be more susceptible to attack from the Cabbage Moth and the Cabbage White Butterfly when conditions are too warm for them or when the soil they are growing in is too acid for their liking, especially while the plants are young.
The cabbage family includes Brussels sprouts, Chinese cabbage, cauliflower, horseradish, kale, kohlrabi, mizuna, mustard greens, swede, tatsoi, turnip, watercress and stock, and is also related to radish. These plants need both boron and molybdenum for healthy growth and these are only available to plants when the soil pH is close to neutral. If you know that your soil is acid, and your Brassica plants are being attacked, give the bed a drink of dolomite or agricultural lime. Dissolve a generous handful in a full watering can and apply this to each square metre of the bed. Repeat the application if pests are still hanging around in two weeks.
In the meantime, remove all pest eggs from under leaves and leave crushed caterpillars on the leaves. This helps to deter further egg laying.