Insects are a valuable part of nature’s balance but they’re not always welcome in the garden. How can you tell a good bug from a bad bug? What’s the best way to prevent an infestation of crop‐destroying insects and how can you attract the beneficial bugs?
Identifying Harmful Insects
Insect pests in the garden include soil‐borne pests such as cutworms and wireworms, and airborne pests such as aphids, beetles, and flies.
Start by learning to identify the primary insect and pest species in your garden. Get a good book on insect and pest control. Some good bugs and bad bugs look very much alike and so it is often hard to learn to distinguish between the two.
Below are just a few common insect pests found in the vegetable garden and suggestions for remedies.
One of the most destructive garden pests is the cutworm ‐ aptly named as it cuts off the stem of the plant at ground level. The cutworm caterpillar ranges in colour from grey, brown, black, red, and greenish‐white to striped or spotted. One way to identify cutworms: if poked with a stick, they curl up into a ‘C’ shape. The adult forms of cutworm larvae are small brown moths often called millers. Millers are very attracted to bright lights and are often seen flittering around a porch light at night. Cutworms also feed and do their damage at night. Prevention is the only cure. The best solution is to put a ‘cutworm collar’ around each plant, which the cutworms won’t crawl over. Collars should be about 5‐8 cm (2‐3″) high and can be made from many recycled materials, such as small tin cans, rings cut from plastic yoghurt cartons or cardboard rolls, or stapled strips of plastic or cardboard. Press the collars securely into the ground. Natural predators for cutworms include birds, toads, and ground beetles. Bats will also eat the adult moths. Biological controls include parasitic wasps and parasitic nematodes.
Wireworms are the larvae of the click beetle, and are thin orange‐coloured worms, pointed at both ends. Wireworms are usually only a problem in new gardens where there previously was grassland. Wireworms feed on grass roots ‐ if there’s no grass, they’ll feed on the roots of your vegetable plants instead. One solution is to dig the new bed in the fall and turn over the soil several times, so that birds can feed on the unearthed wireworms. Beneficial nematodes are another option. Predators include chickens, which will gladly rid your plot of wireworms!
Aphids are sap‐sucking insects that leave a telltale sticky honeydew, which results in plants being covered with a sooty mould. Beans, brassicas, lettuce and other vegetable crops can be infested with aphids. Beware of adding too much nitrogen to the soil, which can be an attractant. One treatment: blast sturdy plants with a strong stream of water, making sure to spray underneath leaves. Aphids like the color yellow: fill a recycled yellow plastic margarine container with soapy water. The aphids will fly in and drown. Insecticidal soap is another option. Ladybirds (ladybugs), soldier beetles, lacewings, and damselflies all eat aphids. Plant basil, chives, dill, fennel, garlic, or mint as a deterrent.
These small black beetles ‐ called flea beetles because they jump like fleas ‐ can cause serious damage. They can kill young plants and eat holes in the leaves of larger plants. Time plantings to avoid peak populations, or plant under cloches or floating row covers. Keep plants well‐watered, as flea beetles are attracted to hot, dry soil. A shallow pan filled with beer will attract and drown flea beetles. Dusting plants with wood ashes or diatomaceous earth are other alternatives. One of the best solutions: interplanting. Flea beetles find their host plant by its scent. The differing scents from a variety of plants confuses them!
Cabbage Root Fly
The white larvae of the cabbage root fly are about 1 cm (1/3″) long and will feed on the roots of all brassicas. Preventative measures include using collars as for cutworms, growing under floating row covers, and parasitic nematodes. Putting wood ashes, diatomaceous earth, or hot pepper around the base of the plants may also help.
Carrot Root Fly
The carrot root fly maggot, or larva, attacks carrots, celery, celeriac, and parsnips. Affected foliage will have a reddish discolouration, and affected roots will have dark spots and tunnels through them. Preventative measures include not adding too much manure to the soil, growing under floating row covers, and companion‐planting chives as a deterrent. These are just a few of the common insects that you may encounter in your garden.