Pest Control for Sago Palm

[tzestan]

I have this sago palm for many years. New shoots are always attacked by caterpillars of a small butterfly species. During early new leaf flush, I can protect the shoots by covering it with a softdrink bottle. The bottom of bottle is cut and covering the upward growing shoots.

As the shoots mature, the bottle is removed. But young leaves are still vulnerable to caterpillars. Over the 1.5 weeks while leaves harden, it is a laborious work hand picking caterpillars. About 50-100 eggs and caterpillars need to be removed daily!

This is manageable at small plant. But now, next flush will generate more than 50 leaf stalks. Hand picking caterpillar will be too time consuming. I am looking for a better pest control method. How are other growers keep this pest under control?