Anita Morton - Growing Gardens
Getting the upper hand
Winter is a good time to treat garden pests with organic sprays, which are non toxic and will be most effective at this time of year. White oil, for example, helps to control scale insects, mites and aphids. Adult scale insects are very hard to kill, and winter spraying with white oil wont necessarily kill them all off. You will also need to spray in November and March to catch all the juvenile insects and keep the plant free of these pests.
For citrus trees, which are very susceptible to both fungal diseases and insect attack, a winter spray with Bordeaux mixture, followed up a month later with white oil, will help to keep the tree healthy. Soapy water sprays are another effective organic way to get rid of aphids and sooty mould. Use cheap soap, and dissolve 100g in a litre of boiling water. Use a couple of tablespoons of the concentrate per litre of water, or enough to make a slightly milky liquid that foams when you agitate the mix.
General garden hygiene such as collecting and disposing of all diseased leaves and twigs is a good idea. Put this material in the bin, rather than the compost heap, to avoid spreading disease in the garden. Plants with loose, flaking bark can also have this stripped off insect pests often hide under loose bark over winter.
The many winter-fruiting trees grown in our area are one of the reasons why we have so many problems with fruit fly. This pest must be controlled throughout the year, as they are active on warm days in winter and large numbers can build up by spring. The hormone lures attract male flies only, but they will show you if theres a problem in your garden, while also reducing the number of breeding males.