Gardening for Predators
She thanked me for my time and we politely parted ways, but I stewed about that conversation for weeks. (Still am, clearly.) I thought about how it was when we'd first moved into our home two years ago, with no plants at all around the house and a discarded sprayer in the shed that attested to the previous owners' dedication to a sterile environment, insect-wise. The place had tons of mosquitoes, ants, beetles and other annoying insects, but no spiders, no butterflies, no large insects to speak of. And so many freakin' mice! Fast forward two years later, and after no spraying and no widespread insecticides, the landscape has changed. There is a wild honeybee hive somewhere nearby, and the bees happily visit the flowering plants. (And yes, I give them a close look to make sure they're not Africanized. They're not, they're tiny.) There are praying mantises the length of my palm, enormous butterflies, wasps (not by the house, though, those nests get knocked down, sorry guys), a ton of spiders, ladybugs galore - all kinds of interesting insects. (Still have mice in the shed, dang it.)
The path from expensive spraying to a peaceful, not-pesky, not-in-your-house insect population is really pretty simple. First, ditch the pesticides. Anything that says something like "Will kill everything!" is something you really don't want around your house. Kill the predators, and shortly, the prey will be back en masse, because they reproduce a lot faster than the predators.
Second, leave them alone and let them do their work. Yes, I know some predators, like spiders, are creepy, but think of it this way: if there is a large spider with a web where you can see it, they're eating insects that would bother you another way. And that means fewer insects for the HIDDEN spiders to eat. So if there's a stable web with a spider in plain sight, leave it alone. (If it appears suddenly in the shower, or ON ME, I too will kill it. Usually while screaming. Hey, no one's perfect.) Some predators, like ladybugs and the praying mantis, can be purchased from local garden stores like Calloway's and Redenta's. Beneficial nematodes are another great biological control to add to your list. Others, like spiders, will just have to show up.
A word on fire ants and wasps. Yes, they are horrible, vicious creatures that I hate for the pain they inflict upon me and my children, but they do have a place in our garden. Fire ants prey on ticks, which carry Lyme's disease. I have to admit, since I've let the fire ants maintain a population on the farm, I haven't seen a single tick. When the mounds get out of control, or when they try to move in too close to the house or a play area, I use the citrus oil and soap solution recommended by Mother Earth News: Fire Ant Control. It's pet safe, child safe, and isn't going to kill other creatures because it's applied just to the mound. Wasps, too, prey on harmful insects such as beetle larvae and caterpillars. Tomato growers, this includes the dreaded hornworm! When the wasps get too close to the house, I just knock down their nest. There are plenty of other places they can build their nests; just not where the kids play.
An important note: there is one insect predator I kill every time I see it, and that is the assassin beetle, or kissing bug. They carry Chaga's disease. CDC Information on Chaga's. They look like an extra-large stinkbug with one enormous fang. Contact A&M for instructions on how to send them in to be tested for Chaga's Disease: KissingBug@cvm.tamu.edu.
Third, plant a predator-friendly garden. Native perennials like asters and coneflowers are favorites of many predators. Some, like wasps, only feed on insects as larvae, and the adults act as pollinators by feeding on the nectar from plants. Many butterfly and bee friendly plants are good options - bee balm, passion flower, sage in all its varied forms, and many kinds of herbs. The "cottage garden" look, with its half-wild, rambly perennials, is a good model for what predators will like - a diverse range of flowers with different blooming times and a variety of structural habitats to suit their needs. Don't bother cleaning out the leaf litter, either; a loose substrate of decomposing plant material gives predators cover as they hunt among the flowers, and it's free compost for your plants, too. Best of all, with a glut of food available outside, insects will have little motivation to invade your home, as long as you keep food and water closed away.
Individual insect problems can be handled as they arise. Aphids mean I need to get ladybugs, and kill the ant mound that is taking care of them. Because yeah, that's a thing. Hornworms can be picked off individually if the wasps don't eat them. Howard Garrett has an outstanding article here on low-impact insect control when things get out of hand.
Forth, get your neighbors on board with a predator-friendly garden program. If your neighbors are spraying pesticides, they will kill predators. YOUR PREDATORS! Talk to them and get them excited about predators. The more of you who do it adjacent to each other, the more effective it will be.
Best of luck to you! May an army of insect predators march forth under your command to eat all the annoying pests in your garden!