Citrus Pests control should involve a combination of methods including cultural and biological and when needed, the targeted use of selective pesticides. They fall mainly into two categories, chewing insects and sap sucking insects.
Citrus Leafminer originally comes from southeast Asia and is now common in Perth. The larvae gets into young foliage in Autumn and eats the leaves creating silvery white tunnels.
The damage can be severe and is mostly seen in plants under 3 years old. The infestation is worse on new growth. The leafminer is naturally controlled by a parasitic wasp, however if chemical control is needed, you can use a horticultural oil from summer to autumn.
Lightbrown Apple Moth
They occur from spring to autumn and are up to 20mm long. They can be found in protected areas or in the navel of some navel oranges. The caterpillars produce a protective web under which they feed. They are controlled by parasitic wasps, however they can also be controlled by pyrethrins.
Mediterranean Fruit Moth
The leafminer is the most common pest in Perth and is the worst between November and July. They can attack all citrus varieties but are most common in mandarins and oranges. They leave small holes in the fruit, indicating where the eggs were laid and these become maggots in your fruit. The maggots tunnel into the fruit causing it to rot and drop to the ground. You can control adults with a weekly baiting of leaves made up of a combination of Maldison as the pesticide and a lure of sugar, honey or molasses, mixed with bran (wet baits are better than dry).Other available pesticides such as Carbaryl can be used as well as organic products such as Spinosad and Neem. If the infestation is heavy you can spray the fruit every one to two weeks when the fruit is half to three-quarter size. This will kill the eggs and maggots, but insecticide residue will be present so you will have to follow the manufacturer’s directions for the suitable withholding period before picking and eating fruit.
Sap sucking Insects
Honeydew producing insects such as aphids, scale, mealybug and whiteflies are closely related, all sucking plant juices from different plants with specialised mouthparts. When eating, honeydew is secreted, a sticky fluid that is a by-product of their feeding. A sooty mould can establish where the honeydew lands. Sooty moulds are fungi that make the plant look like it is covered in a layer of soot. Sooty moulds do not directly affect the plant, but they can interfere with photosynthesis and this, in turn, can stunt the growth of the plant. The fruit is still edible and the sooty mould can be removed with a solution of mild soap and warm water, or white oil is a type of effective chemical control.
Honeydew producing insects are often “farmed” and defended by ants. Ants use the honeydew as a food source while protecting the insects from predators. Controlling the ant population will also help to control the sap-sucking insects.
Black Citrus Aphid
Non-Honey dew producing insects such as crusader bugs, mites and thrips can also be controlled with white oil.