for effective and environmentally friendly caterpillar control my opinion is you can t beat the squashing em with ya fingers method.

most leaf pests tend to target new growth and operate on the underside of foliage. if you tour your garden once a week you ll get to know what the various stages of healthy new growth look like and can then zone in on areas that look stunted or distorted.

caterpillars in particular have a habit of sticking the underside of one leaf to the upper surface of another .

i think a 21st century approach to garden pest control should include an appreciation of the concept of " sub-lethal damamge " meaning a few holes in a few leaves don t cause sleepless nights.

other caterpillars management strategies would include...
checking the underside of foliage for eggs at the appropriate time of year
awareness of moth pollinated flowers
awareness of the moth inviting effects of garden/security lighting
promotion of bat habitats

cant think of anything else...by the way one arm of the computer chair fell off today and it actually makes it much easier to nip to the fridge and back.