I am all for just letting them be, but when they are killing my plants I draw the line.
Earlier this year we had caterpillars invade and eat a fair chunk of 3 Peaches and Cream Grevilleas, and one newly planted Little Spotty Gum to the point it had no leaves left. All but one of the Grev's survived and have bounced back (the other is still struggling and I think it needs to get ripped out and replaced).
I thought it was strange that they left the other 2 P&C Grev's and another Little Spotty alone (which is now double the size of the one which was eaten), which were in between all of the other eaten plants. Maybe the moth/butterfly was just being picky where it lay its eggs.
When I was out in the garden the other day I noticed the same thing starting to occur again but only found one caterpillar (I suspect they are lurking somewhere).
I have read about systemic pesticides that are absorbed by the plant and kill whatever eats it, but I'm not sure if they are ok to use on all plants, and if that may be a drastic measure for something I can fix naturally.
Can anyone recommend something?
I don't think the plants could survive another round of munching.