Cycads   Cycad Blue Butterfly

Scientific Name: Theclinesthes onycha Description: These butterflies have pale brown wings, with a metallic blue or purple sheen, and a wingspan of 25-30mm. They have eye patterns of orange and black on the margin of hindwings, and each has a little tail attached. They lay pale white-blue, disk shaped eggs on the young, soft leaves. The caterpillars are green when they hatch, but become dark brown as they grow older. They hide under the leaves and in the crown, and feed at night. Distribution & Habitat: Its habitat is open forest, in eastern coastal areas of Australia from Cape York in Queensland to southern New South Wales. It is the only Australian butterfly caterpillar that feeds on cycads. It has obviously been around for a long time, but it is only in recent years that it has become a pest.

Figure 1. Cycad Blue Butterfly

Figure 2. Cycad Blue Butterfly

General: It mainly attacks Cycas (all species) and occasionally Lepidozamia, however it doesn't touch Bowenia, Encephalartos, Zamia's or Ceratozamia's. There are reports of it attacking Dioon edule , but not any other Dioons. Its enthusiasm for Macrozamias is unknown (if anyone has any information about that, please let me know). If there are a lot of butterflies around, it is likely they will attack anything they can lay their eggs on.

Treatment: Hose away the wool in the crown before the new leaves emerge. Make up an insecticide, (e.g. Crown, Bugmaster, Rogor, Supracide, Dipel but not a pyrethrum based one), and add a wetting agent (e.g. a few drops of dish washing liquid), to get it to adhere to the leaves. I also add some seaweed to the spray, to feed the plant. Spray the emerging leaves (both sides) and the crown weekly from just before the new leaves emerge and also after rain, and continue spraying until the leaves harden off. (from Peter Heibloem) A good spray for them has the active ingredient of Bifenthrin and is available under several different brand names, and you need to add wetting agent to the spray so that it sticks to the leaves and doesn't just run straight off. A quick and simple remedy is Mortein surface spray once a week in the cool part of the day. (from Will Kraa)

Figure 3. Cycad Blue Butterfly

Another commonly mentioned cure is vinegar. Make up a mixture of a cup of vinegar, in 1.5 litres of water and spray that onto the leaves. However a bit of research on the web suggests that this remedy is of limited effectiveness. On the plus side it is cheap and easy, and also non toxic to most other things, so its probably worth a try initially if you don't have many plants.

 

Contributed by:	Will Kraa
	Peter Heibloem, Cycad Gardens
	Brisbane Insects, (Figures 1,2&3)