Many people think that a bug in the garden is a bad thing, but actually it is not. Most insects in the garden actually cause no trouble for your plants and some are even beneficial!
Although it doesn’t seem like it, the actual number of insects that are detrimental to our plants is pretty low, considering the vast species of insects. This brings us to a question many gardeners have: what insects are beneficial and how do I attract them to the garden?
First of all, there are two types of beneficial insects: predators and parasites. Predators actually hunt down their prey and feed on them, while parasites live on or within an insect.Either way, it spells death to the bad guys! Predators will generally feed on many insects in their lifetime, and parasites generally feed on their prey when they are immature before becoming adults and look for prey to lay eggs on or within.
We will start with predators, which include praying mantis, lady bugs (adults and larva stage), ground beetles (large shelled beetle found under logs, etc.), pirate bugs, syrphid flies (we used to call them steady bees as kids), predatory stink bugs, (which have a large spear shaped mouth and will hurt you if bothered), lacewings (larva and adult stage) and don’t forget the spiders. Out of all of these, the lacewing is probably the most voracious! They will eat aphids, scales, mealy bugs, mites, and all types of insect eggs. Each lacewing can eat over 100 insects per day! These are followed by lady bugs, praying mantis and assassin bugs. Praying mantis and assassin bugs are more likely to take out larger bugs, as they get so large themselves, while lady bugs will concentrate on aphids and mites.
On to the parasites, we will begin with small wasps. There are numerous varieties of wasps that lay eggs on or within insects that basically eat them from the inside out! For all of those tobacco and tomato growers out there, the tobacco and tomato horn worm (large green caterpillar) that you see with small, white egg- looking things attached to its back, this is the work of these wasps. Leave these caterpillars be, as those wasps will emerge from the worm and lay eggs on more caterpillars!
Predatory mites eat a lot of other mites, although these aren’t technically insects, but they do eat bad mites like two-spotted, etc. The predatory mites are the little red dots you see crawling around on pavement, etc. They generally crawl up on the pavement to dry and warm up before going after the mad mites and their eggs!
Now that we have identified some of the good guys, there are some things you can do to attract and keep them in your garden. First of all, don’t spray broad spectrum insecticides like Sevin and Orthene. These kill a great number of insects ,but also kill the good guys. In fact, Sevin will actually stress the two-spotted spider mites and cause them to become worse! You must learn to accept some damage, as there has to be a population of bad guys to attract the good guys!
You need to have a wide variety of plants in the garden and yard to attract beneficials as well. This will allow for an array of insects and habitats to increase diversity and the chances that beneficials will stick around on your property. Although not a good idea for disease control, a patch of weeds or wild areas near the garden is actually good to keep beneficials nearby. It is also a good idea to plant cover crops, perennial flower beds and even a hedgerow to give the beneficials shelter.
Like any other living thing, beneficial insects need water! A shallow pan of water with a rock sticking out, or a bird bath or even a fish pond gives insects a place to get a drink if need be. Be sure to change the water every few days as not to attract mosquitos! This pan of water will also attract butterflies as an added benefit.
It is a good idea to plant 5-10 percent of your garden in plants to attract beneficials. Plants that attract beneficial insects include black locust, caraway, knotweed, cowpea, clover, buckwheat, Queen Ann’s lace, fennel, spearmint, buckwheat, and yarrow. Many of these are weeds, but planted accordingly can be inter planted with flowers and vegetables and will look quite nice.
Other beneficials that many of us don’t think about are bees and earthworms. Honeybees are best at pollinating our fruits and vegetables, but other bees do help out as well. One third of our entire food supply is made possible by these insects pollinating our crops! Again, avoid spraying broad spectrum insecticides and any insecticides while the bees are active.
Earthworms are often times not thought of in any way, but they are one of our best tools in the garden. Did you know they can live for 10-15 years? Each day, earthworms consume their weight in organic matter, making large particles smaller, which allows bacteria and other smaller organisms to break this material down, further fertilizing our plants. They improve soil structure and fertility tremendously.
Earthworms generally are only in the upper two feet of soil and burrow up and down, pulling organic matter down into the ground as they go. They also pull organic matter over the burrow holes to conserve moisture for themselves and your plants. An acre of soil can contain 500,000 earthworms that mix 5 tons of soil a year! That is 5 tons of soil that we didn’t have to touch or think about.
If you have any questions about attracting beneficial insects or organism to the garden, give me a call at the Washington County Extension Service at 859-336-7741. Happy gardening!