Honeydew producing insects are often actively transported, ‘farmed’ and defended by ants. Ants use the honeydew as a food source while the insects are protected from parasites and predators. Controlling the ant population will therefore also reduce these pests. To control ants, send a small sample on a small piece of sticky tape to the Pest and Disease Information Service (PaDIS), for identification and advice on control methods.
Non-honeydew producing pests
Crusader bugs (Mictis profana) are up to 25mm long, with a pale yellow to orange cross on their backs and can spray a stinking fluid when disturbed. They are a native species and can occur year-round. On citrus trees, they feed by sucking on young shoots causing the shoot tip to wilt and die.
They are controlled naturally by assassin bugs (Pristhesancus plagipennis), lacewings, by small wasps which parasitise the eggs and by Cryptolaemus montrouzieri which is a native ladybird known as the ‘mealybug destroyer’.
Mites are less than 1mm in size and often tick or spider-like in appearance. Adults have eight legs. Species like the two-spotted mite are just visible to the naked eye, while other mites such as the brown citrus rust mite and citrus bud mite can only be seen with the aid of a microscope. In Western Australia, two spotted mites and citrus bud mites are the most common. Control bad infestations with sulphur, horticultural soap or a horticultural oil spray.
These mites (Tetranychus urticae) feed mainly on lower surface of leaves causing a typical yellow stippling or spotting effect. Occasionally, damage can also occur to fruit. Two-spotted mites are particularly active in warm to hot conditions and numbers can be reduced by spraying water beneath the foliage. Mite-eating ladybirds and predatory mites are natural control agents. Chemical control is usually not required.
Citrus bud mite
Citrus bud mites (Aceria sheldoni) can attack all citrus varieties but damage is mainly seen on lemons. Active year round symptoms of bud mite damage are distorted flowers, fruit and shoots. The mites usually hide inside leaf and flower buds, making control difficult.
Thrips are small, slender soft-bodied insects just visible to the naked eye. Adults are only about 2mm long. Two exotic species of thrips damage citrus in Western Australia: Kelly’s citrus thrips (Pezothrips kellyanus) and greenhouse thrips (Heliothrips haemorrhoidalis). Kelly’s thrips feed under the calyx of young fruit causing scarring which develops into a distinctive halo as the fruit matures. Greenhouse thrips feed on the leaves, between touching fruit, or where leaves or stems touch the fruit. This results in the production of grey scars or “bleaching”.
Natural predators and parasites of thrips do occur or you can control the pests with sprays of horticultural soap or pyrethrin.
Citrus gall wasp
Citrus gall wasp is a pest of citrus trees grown in backyards and orchards. Citrus tree owners are encouraged to implement control measures on their property to reduce the threat to the citrus industry in Western Australia.
Swollen lumps on the young stems of citrus trees signal egg-laying activity by the wasps. The swellings get bigger as the wasp larvae grow. Please report suspected sightings to the Pest and Disease Information Sertvice (PaDIS). See Citrus gall wasp control for more information.