This is a new one for me - never encountered this pest in my area.

I did a bit of research and all the information recommended hand removal as the most efficient control. Bt was also mentioned, spraying before the caterpillars wind themselves up in their leaf cocoons or by forcefully spraying into the rolled leaf. Bt is a standard treatment for all manner of caterpillar control.

There were no references to any other insecticide but as the larvae drops to the ground to pupate in late summer, you could try applying beneficial nematodes then. These are beneficial predatory soil organisms that feed on insect larvae in the ground and are used for many similar types of insect issues. You just need to be conscious of the proper timing of the life cycle of the insect for application as the nematodes are somewhat temperature sensitive, not long-lived and a tad expensive.