Beneficial insects can help us in the garden in a number of ways, either by dining on plant pests directly ("predators"), or by laying eggs in their larvae ("parasites"). Other beneficials help by pollinating the flowers that turn into our squash, peppers, cucumbers and many other "fruiting" crops. And a few wild species of bees also eat plant pests, not just nectar.
Whether a bug is a "plant pest" or a "beneficial insect" requires a human perspective - a bug either helps or hinders us in our efforts to grow a vegetable garden. But from nature's perspective, the ideal is really a balance which includes both predator and prey insects. It is this balance we are going for in a healthy vegetable garden, not a predominance of one over the other.
The best way to assure a population of beneficial insects is to attract them from the surrounding environment, and if you give them what they need, they WILL come. You may also be able to buy them at garden centers, but in order to get them to stick around and not just fly off, you will need to provide them with:
There are too many beneficial insects for me to provide an exhaustive list, but here is a table showing a few of the most common ones, and what they either eat or parasitize.
|Beneficial Insect||Helps Control|
|Minute pirate bug||a wide variety of small insects, including thrips|
|Big eyed-bug||a variety of small insects|
|Assassin bug||a wide variety of small to medium-sized insects|
|Damsel bug||a variety of small insects|
|Mealybug destroyer||a wide variety of mealybugs and scale insects|
|Soldier beetle||aphids and eggs & larva of other insects|
|Green lacewing||a wide variety of small insects|
|Syrphid fly||aphids and other small, soft-bodied insects|
|Tachinid fly||wide variety of larva (which ones depends on species)|
|Trichogramma wasp||larva of hundreds of species, including butterflies|
|Praying Mantis||a huge variety of insects, including beneficials|
|Predatory Mites||spider mites|
|Whitefly Parasites||whitefly larva|
For color pictures and an encyclopedic reference to beneficial insects, you can't beat the UC Davis website, which has wonderful photographs and details of a huge variety of beneficials and what they help control. They also have a free color poster you can download and print with pictures of some of the more common beneficials.
Most people don't think of paper wasps or yellow jackets when they think about beneficials, but they actually are very helpful because they eat a number of damaging insect pests including cabbage loopers and other caterpillars.
Beneficial insects should be a part of every vegetable garden. While we all like to see those beautiful photographs of perfect beds with perfect vegetables, a really healthy, diverse and balanced vegetable garden should truthfully be a bit messy. Between the compost bins and leaf piles, the mulches and the stuff planted every which way, all mixed up all over the place, it's photogenic in its own, wabi sabi kind of way...
With pots of flowers and herbs here and there. And saucers of water and pebbles. And a brush pile against the fence. And bird baths. And catnip left growing wild because Angel and Nikki like to roll in it. You get the picture. Go wild (at least little)!
But mostly, have fun.
"The unmulched garden looks
to me like some naked thing which for one reason or another would be better off with a few
--- Ruth Stout