July Pest of the Month: Caterpillars

Caterpillars are the larvae of moths and butterflies and are often easily recognised by their long fleshy body and paired prolegs down their abdomen. They are common problems that are sometimes difficult to manage because they hide under leaves, within rolled leaves, inside stems or leaf mines.

Caterpillars damage plants by physically removing plant material and may cause plants to be unsightly with changes to the structure of the plant (e.g. tip borers) and frass and silk deposited.

Small larvae do not cause much damage, but as they get bigger they consume an exponential amount of foliage with large larvae consuming a massive amount and potentially removing whole leaves. As a result, damage can appear to occur ‘overnight’.

Caterpillars can be managed using cultural practices, predators and pesticides (some of which are low risk to predators, parasites and pollinators). For those experiencing difficulty managing caterpillars it may be worthwhile getting the pests identified, particularly if it looks like it is one or a small number of pest species. This may assist in understanding the lifecycle, when the species may be migrating, knowing what hosts are susceptible, where they pupate and perhaps other information that may help to break the lifecycle in the nursery, e.g. susceptible/resistant hosts.

All production nurseries receive 6 free diagnostic samples through Grow Help Australia. Grow help can sequence the certain gene regions of caterpillars to identify them, generally to genus level, but sometimes to species level.

For more information on the biology and management of caterpillars refer to resources at the nursery APPS website including the management plan, fact sheet on stem borers, current minor use permits and many other resources. The pest ID tool also has photos of various caterpillars and moths that may help with preliminary identifications. In addition, Australian Moths Online and has hundreds of photos of pest moths present in Australia (browse or search for ‘Pest’).

Photo caption: Large larvae can consume a substantial volume of leaf material