Aphids are small (2mm) long, soft-bodied insects. There are several species of aphids that are found on citrus trees, including brown citrus aphid, black citrus aphid, melon aphid, spiraea aphids.
Plant Parts: Whole Plant
Season: Spring - Check young shoots in early September - late October and February to April for Summer-Autumn Flush.
Symptoms: Aphids produce a sticky substance (honeydew) as they feed on the plants (similar to scale insects). This honeydew attracts ants and can also encourage sooty mould. In 'payment' for the honeydew, ants protect the aphids from parasitic wasps. Any of these symptoms... honeydew, mould, ants or the aphids themselves indicate an infestation. Aphids can be a threat to young citrus trees by suck sap and decreasing vigour.
Control: You can efficiently get rid of small isolated aphid infestations by simply crushing the insects by hand or pruning the affected area of the plant. Organic sprays can also be applied to the trees (use horticultural/pure soap or garlic/chilli-based sprays mixed with water). Be sure to rinse the undersides of leaves because aphids hide there. For severe infestation, use a spray with horticultural oil (don't apply when the weather is over 32*C as plant leaves can burn) or insecticidal soap like Pyrethrum dust or spray.
Prevention: Be mindful of applying products that will destroy beneficial insects that are natural enemies of the aphid such as lady beetles, lacewings and parasitic wasps as they will devour aphids.
References: Department of Primary Industries NSW, our FST team.
