Insects: our tiny garden friends


You’d think, from the language some pesticide manufacturers use, that most insects spend their days pillaging gardens.  The truth, though, is that up to 90% of insects are actually beneficial to the garden, or benign.  In addition to pollinating plants, breaking down organic matter, and aerating soil, they eat insects that do like to munch on our prized plants.

Broad-spectrum pesticides kill indiscriminately

Pesticides introduce harmful chemicals to our gardens, and kill both beneficial and harmful insects.  When you remove the natural predators from your garden, there’s nothing left to kill the second (and third, etc.) wave of harmful pests that will, inevitably, move in as they pass through your neighbourhood.  So now you have another type of insect to deal with.  You may find your garden is in worse shape than before because the natural predators weren’t there to protect it.

Attracting beneficial insects

A perfectly mowed lawn is not an inviting habitat for beneficial insects.  Gardens that contain a mixture of flowers, shrubs, herbs, and vegetables offer an inviting habitat for beneficial insects, as well as birds, bats, frogs, and toads.

Good bugs

Here’s a selection of bugs that help your garden:

  • Assassin bugs are well-named.  They eat many different types of bugs and their larvae.
  • Centipedes eat pests that live in your soil.
  • Ground beetles eat cutworms, caterpillars, slugs, and snails.
  • Hoverfly larvae eat aphids, cabbage worms and other small caterpillars, mites, and other pests. Adult hoverflies consume flower nectar, and help to pollinate plants.
  • Lacewings eat aphids, whiteflies, larvae, thrips, and mites.
  • Ladybugs, ladybirds, and ladybeetles eat aphids, mealybugs, and scale.  Their larvae eat mites.
  • Spiders, like the yellow garden spider shown above, catch pests in their webs.
  • Parasitic wasps lay their eggs inside pests, thus destroying the pest when the egg is hatched.
  • Pirate bugs eat a variety of insects, such as aphids, spider mites, and thrips.
  • Praying mantis eat a wide variety of insects, such as fruit flies, aphids, cockroaches, crickets, beetles, grasshoppers,  and caterpillars.

Bees and earthworms, it should go without saying, are also insect heroes of the garden!

The bad

Here’s a selection of pests that may damage your garden:

  • Aphids spread viral diseases to legumes, and damage leaves.  They have many natural predators, as indicated above, and can be removed with a spray bottle filled with water or a natural soap solution.
  • Many types of beetles and weevils can damage plants.  The best solution, in many cases, is to remove them by hand, shake them off the plants, or apply floating row covers to your plants.
  • Adult Japanese beetles eat flowers and leaves, and their larvae attack roots.  The best defence against them is to apply row covers to your plants.  You can also try applying a spray made of cedar oil.
  • Borers, as the name implies, bore holes in stems, which causes wilting and then death.  They attack plants such as melons, cucumbers, and squashes.  You can carefully cut them from the stem with a knife and then place the wounded part of the stem under the soil to encourage it to heal.
  • Caterpillars may eat plant foliage and fruit, and sometimes their roots.  Pick them off and destroy them.
  • Earwigs like to burrow in peppers and corn cobs and eat the tips of buds before they flower.  There are many ways to trap them, as they like small spaces.  They are nocturnal so you can empty the traps during the day.
  • Millipedes damage potatoes and may eat seedlings.  They like soil that is rich in organic matter, so be sure to regularly cultivate your soil.
  • Scale suck on plants and leave tiny bumps.  Remove these damaged parts and destroy them.  A soap and oil spray is effective against them when they are in their crawling stage.
  • Slugs and snails eat leaves and small seedlings.  They’re best controlled by birds and frogs, but you can also set traps for them.
  • Thrips suck sap from the upper leaf surface, and they may damage flower buds and prevent them from opening.

The variable

  • Ants aerate the soil and clean up debris and weed seeds, but they also consume the sticky substance created by aphids, and thus transport pests between plants.  If the aphids are controlled by the beneficial insects mentioned above, ants should not be a problem.
  • Nematodes are microscopic insects.  Some varieties feed on insects, and others, such as root knot nematodes and potato cyst nematodes, damage plants.  Crop rotation can prevent these from taking hold in your garden.

It’s not as dire as you think

Sure, there are a lot of insects that can harm your garden, but if you rotate your crops, attract beneficial insects and animals, and practice companion gardening, you’re likely to avoid most of them.



Rotating crops

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Unless you grow plants exclusively in containers, it is important to change where you sow your crops each year.  Rotating plants protects them and improves the nutrition that they have available to them:

  • Disease organisms and insects that are harmful to a particular plant may build up in the soil over time, leading to crop failure should the same plant be sown in that same area.
  • Some plants may consume more of one nutrient than others, leading to soil depletion and crop failure should they remain in the same area year after year.
  • Some plants, such as legumes, benefit the soil.  Moving them around helps to improve the soil throughout the garden rather than in just one spot.

How it works

The easiest way to rotate your vegetables is to put them in groups (keeping the principles of companion gardening in mind), and then rotate the groups.  The most common grouping scheme employs the following four groups, although you may choose to use more complicated groupings if you have a large garden or a large variety of plants:

  1. Legumes, which restore nitrogen in the soil, such as peas and beans, as well as potatoes.  Potatoes are root vegetables, but they can suffer from the same blights as tomatoes and other fruits, so we do not want them to follow each other.
  2. Leafy plants that quickly use up nitrogen, such as cabbage, greens, spinach, herbs, broccoli, and corn
  3. Fruits, such as tomatoes, peppers, melons, eggplant, and squash.
  4. Light feeding roots, such as carrots, onions, garlic, and rutabaga.

So here is how we would rotate our vegetables:

  • Leafy plants go where the legumes were the year before, because they need a lot of nitrogen.
  • Fruits follow the leafy plants because they need the phosphorus that the leafy plants provide, and too much nitrogen stifles the growth of their fruit.
  • Roots follow the fruits because they need the potassium that the fruits provide, but less nitrogen.  They don’t like rich soil.
  • Legumes follow the roots to put nitrogen back in the soil.  They also like that the root crops loosen the soil.

So, if you split your garden into four sections, you could plant each section with one of the above-numbered groups, using the following four year schedule:

  • Year 1: 1234
  • Year 2: 2341
  • Year 3: 3412
  • Year 4: 4123

If you use raised beds or planters, and change the soil yearly or so, you may not need to rotate your plants.  Some plants, such as lettuce, have few pests, so they can remain in the same place for a few years if you have a smaller garden.




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