When there are hundreds of insects attacking a plant at the same time, using some sort of insecticidal spray may well be necessary. But if the damage is caused by a small number of insects, hand picking the culprits can be as effective and as fast … in fact, it’s usually faster.
For example, many butterflies only lay a single egg per plant, so the caterpillar you see chomping on a leaf is actually all alone. If so, why spray? Just knock it to the ground and crush it. Or hand pick it and squish it between your thumb and finger (yes, you’re allowed to wear garden gloves!). If you’re a bit squeamish, drop the intruder into a bucket of soapy water.
No potentially toxic pesticide is needed, so you can rightfully feel the impact on the environment is minimal.
Sometimes the simplest solutions are the best ones.