Many aphid species are monophagous why not raise these as food for predatory insects?
I have a number of plants that others consider weeds. I keep these plants in my garden because they are LOADED with aphids.
Thousands of black, red, etc. aphids growing all over these plants. What I have found is that many predatory insect larva need prey to survive.
These aphids provide the nursery for predatory insects. Also plants that are attacked and damaged tend to attract predatory insects.
So I breed plant specific bad bugs to keep an active high population of predatory insects going.
When I put in my annual plants I tend not to have a big population explosion of bad bugs because I already have a healthy population of predatory insects.
Aphids seem to make an ideal predator food because:
"Aphids have a world-wide distribution but there are far more species in temperate zones, we have more than 500 species in the UK while there are about 1350 species in North America. Most aphids are monophagous, though some feed on more than one species of plant, species like Myzus persicae which feed on a number of different plant species are very rare. "
Here is an example. In Ohio where I live I have goldenrod and Uroleucon nigrotuberculatum, which are red aphids (so they are easy to spot on a goldenrod stem). This is a relatively rare aphid that feeds on tall goldenrod species.
However when I read garden blogs I get something like this:
"I have a plant near my fence that was just identified in this site as Goldenrod. It is loaded with red bugs that I believe are aphids. What should I do about that? Don't want them to get into all my garden plants. "
Common reply is:
"I would start by blasting them off with the hose, then if you miss a few hit them with some insecticidal soap. You'll probably need to repeat the treatment a few times--you always miss one the first time and they reproduce at the speed of light so if you don't keep an eye out and repeat the treatment they'll be right back before you know it."
or something like
"I use this product called Dr. Bronner's Magic Soap...a pure castile soap made with peppermint and organic oils that I get in my supermarket. Right on the bottle it mentions that it can be use to kill insects. I made some up to kill ants in the pantry originally, because it is non-toxic for that area. So I used it on the aphids and it killed them instantly."
I even get this type of response from people who are in "Master Gardener" programs.
In the eyes of many gardeners the only good aphid is a dead aphid. But what are lacewings, ladybugs, etc larva to eat if you remove all their food. Also it takes time for a predator population to respond to an increase in food. Bad insects can do alot of damage before their populations are checked.
It is something that I will be working on incorporating in my plant plant this year. I have certain insects which seem to infuriate me to no end (flea beetles that absolutely obliterate my eggplants) and I have been doing some research to see what I can use as decoy plants for them and what I can plant to attract their predators.
"Turn your face to the sun and the shadows fall behind you." ~Maori Proverb
Flea beattle enemies include microscopic braconid wasps, beneficial soil-dwelling nematodes, and a tachinid fly.
Nematodes are effective for the larvae of flea beetles which are small, whitish, delicate, cylindrical grubs. You can purchase predatory nematodes from a number of sources.
Microctonus vittatae is a native braconid wasp found more commonly in the eastern half of the U.S. M. vittatae not only kills the adult flea beetle as the wasp emerges, but the larval wasp sterilizes the female flea beetle while developing in her body.
Floating row covers or other screening can exclude the beetles during seedling establishment. However, remove row covers before the flowering stage to allow pollinating insects access to the plants.
Vacuum beetles off leaves.
Plant a highly favored crop such as radish before you plant your main crop, in an effort to attract flea beetles away from the main crop. Adult flea beetles will be attracted to the tallest, earliest crops available.
Once beetles are actively feeding in the trap crop, they can be sprayed with a labeled insecticide, treated with nematodes to kill larvae or simply harvested to deprive larvea of food.
Disperse radishes around the garden. Flea beetles favor radish leaves. They usually cause only minor leaf damage, but the harvestable root is unharmed and the flea beetles leave the adjacent plants alone.
I have read that if you plant callendula flowers it can act as somewhat as a distraction for many aphids. sunflowers also attract aphids which ants tend to favor, they make good landing spots for some predatory wasps as well, milk thistle can also attract aphids as well.