June: Oh, no! Your tomato plants is all beat-up. They are missing their leaves, stripped bare of stems, and have holes right where the fruit should be. Panic sets in… And so does the impulse to spray like mad all around, with whatever strongest chemical happens to be handy. Don’t do it.
Unless you know what’s bugging you, most of them aren’t out to get you at all, they’re simply having a meal. Knowing whether they are harmless or harmful means you has an identification guide or chart nearby for a quick ID. Knowing the habitat of larvae (where you’re seeing them) is step one. The quickest hint in the field is host specificity.
How to Tell Good Bugs from Bad Bugs
For example, you might see a striped caterpillar on a milkweed. Odds are it’s a Monarch. Leave it alone. You will lose some leaves to help it survive, but you will gain a butterfly that travels thousands of miles during migration. Do you see green inchworms on your cabbage and kale? Those is most probably Cabbage Loopers or Imported Cabbageworms, which don’t migrate at all, and will devour those brassicas in short order. That’s when knowing the difference means you have to move from just watching them to actualy taking action.
Not only what plants they’re on, but how those plants look also can be clues. Examine larvae’s skin texture. Some might be smooth and harmlessly to touch, while others has spines that can cause irritation. It is safe. Are they hairy or bumpy with spines (like this)? Not so much; these will irritate your skin. The chart points out examples, such as larval form of the io moth. Its back is realy more green than brown, but the rest of its body is spiky with branched spines topped in black. Those are no aesthetic feature but defensive weaponry. Don’t touch them bare-handed.
At the opposite extreme are fuzzy larvae such as Woolly Bear, which become Isabella Tiger Moths and aren’t any danger to anything growing except themselves. Knowing which ones sting means knowing when not to worry…or be overly careful.
Timing is another clue. Not everything is around all season. For instance, tent caterpillars make their webs in tree forks as leaves unfurl, and then by high summer they are mostly pupae underground. Hornworms comes into view in mid-summer, coinciding with tomato fruit set. If you have webbing in August, it’s probably not Eastern Tent Caterpillar but perhaps Fall Webworm. Knowing the time of year narrows your guesses without having to examine any color clues yet.
So if you do need to manage things, begin simply: With big larvae (think Hornworms), handpick; they’re easy to see, slow-moving, and easy to pick off. With small pests on leafy greens, use a row cover to create a physical barrier to prevent moths from laying eggs. Better yet, don’t let them in at all instead of having to pick them off later. There is biological controls, Bt sprays or parasitic wasps… To address certain pests specifically, not harmful to other insects. And then there’s broad-spectrum chemical spraying, which hardly ever targets just what it is intended to… Last resort only.
Nobody wants a bug-free, sterile garden. Nobody. But we want an ecologically balanced one where we get to pick our own dinner instead of losing out to pests. Know which ones are helping (even as larvae). That Monarch caterpillar isn’t the same creature than that flying beauty called a monarch butterfly…but she’s part of its life cycle. When you learn what those links are between adults and larvae, you’ll have less battle in the garden and more work going on there. You will have less fear and more strategy. You will have whole tomatoes until someone else eats them.