You must be in Australia. Here in the US, we have a product called BT, which is not really a poison, but it kill caterpillars really well. I'd use that on the plant to see if it works.

BT is a bacteria (Bacillus thuringiensis) that attacks caterpillars, it's available in Australia but I've never used it. That Cycad Blue Moth is apparently common on the east coast but luckily we don't seem to have it here. BT (sold as Dipel here) is supposed to deal with the caterpillars quite effectively.