Attracting predatorial insects to our garden using flowers is an effective pest management strategy. Flying insects such as wasps, hover flies and lady beetles find nectar and pollen for themselves while hunting for protein-rich foods in the form of caterpillars, aphids, and mites for their underdeveloped young. A healthy food source and a toxic free habitat are like billboards advertising to preying insects our desire for them to make a home on our property.
Unfortunately, many of us are unaware of the predatorial pest control team that works and lurks under the plant canopy, roaming around the on the surface and tunneling underground in search of prey. Speedy centipedes, stealthy spiders, and ferocious members of the beetle family all hunt for their food unnoticed and underappreciated.
I became more aware of their importance while harvesting herbs last summer. I was hunched over cutting parsley when out of the corner of my eye I noticed a shiny black beetle making its way across the woodchip pathway. In its vicelike jaws it dragged a half-inch slug. Walking backwards, straining under the burden of its struggling, slimy victim it moved towards the shade of a horseradish plant. Once under cover, it unceremoniously gnawed the hapless creature with it’s giant mandibles while secreting digestive juices. I was transfixed.
Consulting my beetle field guide I discovered that this was none other than Carabus Granulatus, a fierce beetle that feeds on slugs, snails, cutworms, wireworm, earwigs, and caterpillars. It’s one of many species of predatorial ground beetles that you’ll find in a healthy garden ecosystem.
Ground beetles, centipedes and spiders are to our gardens what bears, cougars and wolves are to the forest. They’re fast, aggressive, have a big appetite and help keep prey populations under control. They’re the alpha predators of the soil food web sometimes consuming their own body weight in food each day. They also provide us with incredible fertility as they shed their exoskeletons, go through metamorphosis, and excrete nutrient rich frass for our plants. Let’s do everything we can to attract them to our growing space.
The first and most important thing to remember is to practice minimal soil disturbance in your garden to maintain a healthy habitat for surface dwelling and burrowing insects. Rototillers in the garden do as much damage to their homes as tornados do to ours. We might survive a hurricane, but our dwellings and food will be destroyed. And by the time beneficial insects rebuild and repopulate, a full year has come and gone, and the tiller is ready to make its next pass over the garden.
Second, mulch generously with nutrient rich, coarse compost to provide cover for your garden companions. You’ll notice that most predatorial organisms in our garden when disturbed will scurry for cover under leaves, stones, and woodchips. These chunky bits also ensure insects maintain adequate moisture and protection from the sun and hungry crows and starlings. It’s also where they’re most likely to find their food. I like to use partially composted woodchips that have been decomposing for at least one year. Many carnivorous insects also eat fungi that grows on the woodchips that we add to our garden. In some of the gardens around my house, I’ve also added stumps that slow break down and provide excellent cover for the myriads of the insect that I want to attract to my garden.
Third, try to maintain a cover of plants throughout the year. Some insects can live several years and need shelter to overwinter. Others, need a protected environment for their eggs or underdeveloped larvae. Plant cover provides protection from the sun, moderates temperature extremes, prevents erosion and habitat destruction and attracts a food source. I also highly recommend that you plant perennial crops in your garden including herbs, shrubs and small trees. These are highly sought after environments for beneficial insects who often prefer established plants with more sophisticated root systems and mycorrhizal associations. Their branches and trunks also provide a home where the good guys can hang out.
Finally, I’d be remiss if I failed to mention the importance of keeping the surface moist during the heat of the day throughout the summer. Water to cool the surface of the soil to provide a favourable environment for both your plants and your garden helpers. It’ll bring them out of hiding and encourage them to hunt pests that feed when the sun is it’s hottest.
This growing season I encourage you to spend more time on your hands and knees in your garden observing what happens on the understory of your plants and on the surface of the soil. You’ll be amazed at the entertaining battles that unfold between the hunter and the hunted. Use a bug guide to identify the helpful participants in the garden to build appreciation and familiarity and note what environments they prefer. Avoid soil disturbance at all cost, cover the ground with decaying plant materials and keep a living plant cover to build habitat for preying insects. Building a healthy garden ecosystem is as important to the organic grower as planting, seeding, and harvesting. It’s a worthwhile investment and will help you grow better food while controlling troubling pests.
According to Dr. John Tooker, Pennsylvania State University Entomologist; ground beetles are the lions of no-till and cover cropped fields. Ground beetles consume the five major pests found in no-till fields: black cutworms, true armyworm, corn stalk borer, wireworms, and slugs. Ground beetles and fireflies are major predators of slugs but they also eat caterpillars, aphids, and weed seed; consuming their body weight daily in these agricultural pests. Slug eggs are a favorite food of these predator species, helping to keep slug numbers under control. Tillage strongly influences soil dwelling insects. While tillage may reduce slug numbers by 80%, it also destroys the predator’s home and usually the slugs can repopulate faster than the predators. No-till plus cover crops supports higher populations of predators and decomposers by providing a stable food source, shelter, and habitat that promotes a resilient environment for predators.
- Conserve moisture and moderate soil temperature
- Break up water droplets and reduce compaction
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