Garden Bugs in Ontario, Canada

Ladybugs can be a gardener's best friend.

Ontario gardens are home to a vast number of insects, not all of them harmful. Damage done by harmful insects is always easy to notice. Look for holes in leaves, browning leaves, froth on stems and/or spy the little creatures on the underside of leaves. One way to control harmful insects is to encourage beneficial ones like ladybugs that enjoy eating pests. Toads and birds can also keep the bad bug population down. Another way is to make sure that your plants are healthy by feeding them compost, which helps to protect them and ensures good air circulation between bushes.

Holes in Leaves

Butterflies may be beautiful but their caterpillars can denude a plant's leaves.

Ontario is host to many caterpillar larvae, sawfly larvae, flea beetles and leaf-cutting bugs that leave holes in leaves. Sawfly larvae can completely defoliate such Ontario plants as Columbines, Solomon's seal, gooseberries and currant bushes. Flea beetles can be blue, yellowy-brown or black with stripes and are shiny. Their chewing can turn young plants brown and kill them. Cover plants with row covers to help prevent flea beetle damage. Pick off caterpillars if it is a light infestation or spray with an insecticide if necessary.

Insects on Leaves

Aphids often attack rose bushes.

Roses are a popular flower in Ontario and are popular with aphids as well. Aphids come in many colors from green to brown and can suck all the vigor out of plant shoots. Dislodge the critters with a sharp jet of water or spray them with insecticidal soap. Red lily beetles are also commonly found on lilies in Ontario. They look similar to ladybugs but without the dots. If unheeded, they will eat through all the lily leaves. Picking off the bugs and crushing them underfoot is effective.

Pests on Stems

Spittlebugs, borers, mealybugs and scale insects are some bugs that infest Ontario gardens. You can notice spittlebugs by the distinctive white froth that can be seen on stems on which they are feeding. They are unsightly but not deadly to the plant. Some insects lay their eggs in cracks in tree bark, and their resulting grubs feed on the delicate new stems. These borers are difficult to control but insecticides may help. Mealybugs can be controlled with insecticidal soap spray, and dormant oil that is spread on trees during the winter can protect against scale.

Sap-Feeding Insects

Protect your apple trees with winter dormant oil.

Whiteflies, psyllids and suckers are insects that feed on sap in Ontario gardens. Psyllids and sucker adults resemble aphids and enjoy feasting on apples, pears and boxwood. Immature plants may be stunted if these critters are not controlled. Use dormant oil in winter for apple trees. Other plants may require a pesticide. Whitefly nymphs, which are the immature insects, look flat and resemble scale. They coat the plants with honeydew and this attracts blackish mold. Insecticidal soap sprays can help wither these insects or try planting French marigolds, since their smell appears to be a deterrent.

References

• McGill: Managing Troublesome Insects in the Vegetable Garden; George Bushell
• "Gardening Manual of Canada"; Editor Trevor Cole; 2006