In our gardens we have both beneficial and harmful insects and it’s important that we differentiate between them. Indiscriminate use of a pesticide – too much, wrong material or wrong timing – can harm our garden more than help it.
Pollinators, of course, are indispensible. Other beneficial insects fall in two categories, predators like Lady Bug beetles which feed on various aphids and other small insects., and parasitoids.
Parasitoids are species whose immature stage develops on or within a single insect host, ultimately killing the host. The large green tomato hornworm caterpillar that can quickly defoliate a plant. Sometimes they appear to have many small white cocoons growing from them. That means that a tiny wasp bored into the worm’s body to lay her eggs and the larvae have been devouring the caterpillar from within. They’re getting ready to hatch and continue their beneficial work.
And then there’s the praying mantis that devour anything they encounter, good or bad, so their net contribution is probably negligible. But they’re interesting to have around so most of us call them friends, not foes.
Bottom line: gardeners should identify any insect before they take any action. A good insect identification guide is an important tool to have in the shed.