Above: The kitchen gardens at circa 1730 Salem Cross Inn in West Brookfield, MA. Colonial farmers knew that food gardens interplanted with lots flowering plants helped keep pests under control.
Walk into any hardware or big-box store and you can take home a variety of cheap but toxic concoctions that will kill upon contact. Although this might stop some of the pests for the moment, spraying ultimately does more harm than good. Crop pests are well-adapted to the various poisons farmers have used for decades, and they'll usually stage a quick comeback. Not to mention, do you really want to use increasingly complicated chemical compounds — mostly untested for long-term health impacts and their interactions with other common chemicals — on the food that you eat?
Above: If you spray for pests, you're also killing the natural predators of the pest, such as this hoverfly (aka syrphid fly), a common non-biting fly that visits flowers for nectar - their larvae eat large numbers of our garden pests.So how can you grow food without resorting to harmful chemicals? It requires a bit more thought than just just spraying something from a bottle, but it's not complicated. Basically, you enlist the help of the natural world...and tap into its natural checks and balances.
Above: Vegetable gardens at Tower Hill Botanic Garden - colorful, whimsical, functional, and "friendly" to the "good bugs" that eat garden pests.When dealing with pests, think prevention, not cure. Here are a few Golden Rules:
Provide habitat for beneficial insects and birds who are natural predators of your garden pests. Give them what they need, and they'll help keep pest populations under control.
Confound pests by companion planting your vegetables with plants with strong scent or other characteristics that confuse or repel pests, and rotate crop plants from year to year to stay one step ahead of pests.
Grow your plants in healthy, living soil that is rich in beneficial soil organisms - healthy soil means healthy plants that can withstand a bit of pest damage. Avoid synthetic chemical "power" fertilizers that kill soil life - these actually encourage the sappy, weak leaf growth that attracts pests.
Above: Ring your beds with single-flowering marigolds (Tagetes spp). The bright, nectar-rich blooms attract beneficial insects right until first frost. Plus, the strongly-scented foliage seems to repel (or confuse) many pests, and they are less likely to find your plants.The nectar found in flowering plants is what keeps those insects flying - it's the fuel that keeps them patrolling your garden for pests, so make sure there's something blooming all through the seasons to keep them fed. Yes, some flies are pests and certain wasps do sting, but most of the bugs flying out there are beneficial - preying on other insects, pollinating plants, and as a food source for other wildlife.
Check out this braconid wasp, which is in the process of laying its eggs inside a gypsy moth caterpillar - which means this caterpillar is doomed:
Photo by Scott Bauer/USDA Agricultural Resource Service (Courtesy of bugwood.org)You don't have to worry about these wasps hurting you - they don't have a hive to defend and they don't sting! If you grow tomatoes, you'll want to attract another type of braconid wasp that uses tomato hornworm caterpillars as its host:
If you are reading this because you have problems with hornworms skeletonizing your tomatoes, resolve to start adding plants for parasitic wasps for next year's tomato crop. They'll do a fine job keeping the hornworms under control for you.
Above: Rudbeckia and great blue lobelia bloom their heads off in the rich soil next to our veggie beds - at the same time attracting lots of parasitic wasps and flies who prey on garden pests.
Other common predatorial bugs that you want to attract to your habitat include assassin bugs, ambush bugs and certain types of stink bug, who feed on insect eggs, caterpillars and other creatures that can harm plants. You'll find all of these in and among flowering nectar plants, weeds and wherever bugs hang out.A garden buzzing with insect life also brings in the "big guns" of bug control, including birds, dragonflies, bats, amphibians (toads & frogs) and other wildlife whose diet consists largely of flying insects and/or insect eggs, caterpillars and grubs. Healthy local populations of these predators will cut WAY down on your pests:
Above: Nesting boxes for birds and other winged wildlife at Garden in the Woods, Framingham MA. Nesting birds can feed their hatchlings hundreds of caterpillars every day, so provide them with nesting opportunities near your gardens.Include some locally native plants in your landscaping- these are best for attracting nesting birds because they tend to support the most diversity in herbivorous insects — in other words, plenty of caterpillars to feed hungry baby birds! Even if you don't like the taste of cilantro, parsley, fennel or dill, always try grow lots of these culinary herb plants - they are cheap and easy to grow from seed, and make good companions for tomatoes. Allow some plants to flower - their clusters of numerous tiny flowers (called umbels) contain individual portions of sweet nectar for small beneficial insects. These fellow members of the carrot family of plants are also a host for the caterpillars of the beautiful black swallowtail butterfly:
Don't kill these caterpillars! They turn into beautiful butterflies. Give them their own patch of dill or parsley to eat, or relocate them to queen anne's lace or wild carrot plants.
The tiny white flowers of cilantro attract parasitic wasps and many other beneficials:Leave some areas of bare ground in the vicinity of your vegetable beds to provide nesting opportunities for squash bees (important pollinators of squash and cucumbers) and other native bees that excavate tiny tunnels in the ground to build their nests:
Above: Nesting block for bees and other insects - showing telltale signs of use by mason bees, grass-carrying wasps and other beneficial insects.
Above: Bumble bees are crucial pollinators for many food plants such as tomatoes and blueberries. Although they do raise a communal hive, they are very gentle and won't sting unless physically threatened. Give them lots of nectar plants (right through the season) and a place to nest near your gardens.Problems with slugs? Slugs LOVE the moist conditions of well-mulched, well-watered vegetable gardens and can decimate plants in just a few nights of feeding. Bring in the toads - who hunt the soil at night for slugs, grubs and worms - by giving them a cool, damp place to spend their days:
Give slug-gobbling toads a "toad abode"Feed the soil, not the plants! In other words, provide habitat for the soil food web, or the (mostly micro-biotic) wildlife that lives in the soil. Each year, amend your vegetable beds with compost, farm-animal manure, leaf mold, seaweed or fish-based fertilizer - whatever you can get your hands on locally:
Pests tend to attack stressed plants. Encourage healthy plants by amending your soil with good quality compost (above) and mulch well with organic materials to help retain soil moisture and build soil tilth.
Below: These raised veggie beds on our small Massachusetts farm may look a tad weedy, but the surrounding plants attract so many beneficial insects and bird predators that pest damage is minimal.