I tend to have a very natural approach to insect pests. I don't spray or use anything toxic. When my kids were little I wanted them to be able to just pick something out of the garden and eat it. Safe was more important than keeping my plants alive. So I let many of the bad insects live. When you let nature take its course sometimes good things happen.
This year I had a huge infestation of aphids. Usually they aren't all that bad. So first the lacewings came and laid lots of eggs. In the last couple of weeks I have seen a lot of lady bugs. In due time these plants will take care of my problem. I also plant decoy plants just for such things. The aphids love my borage. So they went there first and my tomatoes weren't quite as infested. My feverfew on the other side of the garden also makes a great decoy.
Every garden has its own issue with bugs. One of my worst issues is slugs. I've dealt with them in a couple of ways. The first and foremost is to hand pick. They are nocturnal creatures usually so I pick them either at night with a flashlight or early in the moring. Some people hate the slime. I've become inured to it. This year they were constantly chomping down my little cucumber seedlings. So I hand picked. I put a ring of crushed eggshells around them. I covered the area with used coffee grounds and I was persistant. Every week I would grow some more seedlings to replace any that were eaten. Slowly but surely I've gotten plants that are big enough to withstand the onslaught. If we would ever get any warm weather the cucumbers will take off.
This year the fireflies have been very active. As far as I know they don't eat anything in the garden, but their progeny, the glow worm, does. They eat slugs. Yes a predator that eats my slugs. I love it. I don't like that they eat my earthworms too, but I have plenty. Yesterday the fireflies were all over the garden. They kept flying into me as I worked.
Last year I had a fight with squash vine borers. They killed all my pumpkins. I didn't get one fruit. This year I'm growing mostly Cucurbita moschata which is resistant to the borer. Sadly there isn't really a zucchini that is resistant. Tromboncino is the closest resistant squash to a zucchini, but it isn't quite the same. Maybe if my zucchinis all die this year I'll try it next year. Last year my zucchini did OK.
For my brassicas I always use a row cover. I can't get them to grow here without it. It looks very ugly in the garden, but if it means I can have cabbage and Asian greens, I'll use it.
For my nematodes I use marigolds as companion plants. They keep the population down. I have them around my corn and my tomatoes.
There is one insect that I've pulled out the guns for though. It is the earwig. Often earwigs aren't bad in the garden. They are predators themselves. They can eat things like aphids and baby slugs. But they are omnivores. They eat rotting material and much like sow bugs when they get numerous they eat plants. Right now I have some infestations in my lettuce. They love hiding in the leaves and they can shred it to pieces if there are no insects to eat. They are also in the tips of my corn. The tips have the male flower starting to come out and they are eating it. Ack! I've also found them in my peas, but so far they have stuck to the aphids and are leaving the plants alone so there they stay.
Earwigs freak me out. Give me a slug any day. They can hide in small places and are hard to catch. So today I brought out my diatomaceous earth. DE is the fossilzed remains of diatoms. It is basically rock that is very sharp. It kills chitinous insects by drying them out. It is innocuous to humans unless you breath it (use a mask). I'm hoping it will help my earwig issue. I sprinkled it down into my lettuce heads and into the tip of my corn. I tried to keep it away from anything else. I don't want my ladybugs dying. Luckily I've never seen them on my corn.
If you think ahead earwigs can be controlled by traps. They love to hide in small sections of old hose. You can shake them out into soapy water whenever you find them. Last year I had two T posts together and they love hiding between them. I would kill them every couple of days. I didn't think ahead this year. So had to resort to DE. Which reminds me. Where are those old hose sections I had? I ought to get them out in the garden.
I've only resorted to three pesticides in my garden. DE is the first. Years ago I used to use a soap spray for aphids, but now I just let them be. The last is Bt (Bacillus thuringiensis). Bt is a bacteria that is specific to killing caterpillars. It won't affect anything else in the garden. Right now I keep all my brassicas under a row covers so haven't used it. Next year I will. I planted some blueberries and found out that the winter moths that have inundated the area love blueberries and eat all the flowers buds off. Next year I'll spray my blueberries when they caterpillars start to hatch.
So there you have it all the things I use in the garden to control insects: decoy crops, companion plants, row covers, hand picking, traps, natural predetors, DE, and Bt.