We know that not all bugs are bad. But can you identify the good ones?
When making crop production management decisions, consider beneficial insect populations. These harmless bugs can provide adequate control if their populations are high enough.
Some beneficial insects are hard to identify, but with some basic training producers should be able to spot them in the field. The following beneficial insects are found in most crops in Western Canada.
1. Lady beetles
There are 160 species of lady beetles in Western Canada.
Identification tips: Possibly one of the easiest beneficial insects to identify, the adult lady beetles generally have a spotted pattern on their forewings.
What they eat: Lady beetles mostly feed on aphids. However, if aphids are scarce, they will also feed on the eggs of moths and beetles, and on thrips and mites.
How much they eat: According to one Manitoba study in cereal crops, the number of aphids a lady beetle can eat depends on both the species of the lady beetle and the aphid. But, for example, the thirteen-spotted lady beetle has been seen to consume between in 110 and 160 aphids in just 24 hours.
Lady Beetle Larvae
Identification tips: While most people can easily recognize a lady beetle in the field, most don’t recognize their larvae. Larvae are alligator-like, and are black with white, yellow, red or orange markings. Common lady beetle larvae in many areas of Western Canada are the seven-spotted and multi-coloured Asian lady beetles.
What they eat: They can consume large amounts of aphids.
How much they eat: In the older larval stages some species can consume over 100 aphids in 24 hours.
2. Ground beetles
There are 861 species of ground beetles in Canada and about 40,000 worldwide.
Identification tips: Ground beetles run rapidly when disturbed. Their head is narrower at the eyes, and their front wings may have striations or pits.
What they eat: Ground beetles eat the larvae of cutworms and diamondback moth; Colorado potato beetles and root maggot eggs, larvae, and pupae; and aphids.
How much they eat: If given the opportunity, ground beetles — both adults and larvae — will eat many times their own weight in prey. They are nocturnal feeders.
There are about 500 species of hoverflies in Canada. Larvae are especially good for aphid control.
Identification tips: Adult hoverflies resemble bees or wasps, although they only have one pair of wings. Black and yellow stripes can be seen on their abdomen. Larvae are often green or brown and tapered towards the head.
What they eat: Larvae eat aphids and small caterpillars.
How much they eat: A single hoverfly larva can eat up to 400 aphids, depending on the species of hoverfly and aphid. Adults can be seen hovering over flowers; they feed on pollen and nectar, making them good pollinators.
4. Damsel bugs
There are 12 species of damsel bugs in Canada.
Identification tips: Damsel bugs are long and slender and have enlarged front legs.
What they eat: They eat aphids, moth eggs, small caterpillars, leafhoppers, mites, lygus bug and nymphs. Damsel bugs can be important predators of the diamondback moth, as well.
How much they eat: In a laboratory study, female damsel bugs were found to kill an average of 131 eggs or 95 diamondback moth larvae in just 24 hours.
5. Minute pirate bug
There are 41 species of minute pirate bug in Canada.
Identification tips: Adults are oval, black with white markings and range in length from three to five mm. Nymphs are orange to brown.
What they eat: Minute pirate bug eats insect eggs, small caterpillars, thrips, mites and aphids. Some species provide great control for soybean aphids. Minute pirate bug also feeds on pollen and plant juices, which means they can survive even when prey is absent.
6. Green lacewings
There are about 25 species of green lacewings in Canada.
Identification tips: Adult lacewings are green and have wings with veins that look like netting. They have gold eyes. Larvae are alligator-like, cream coloured with brown markings, and have sickle-shaped mandibles. They also have long bristles coming out from their sides. The bristles collect debris and food remains, including the skins of aphids.
What they eat: Lacewings eat aphids, thrips and mites. They also eat the eggs of many insects, including leafhoppers and Colorado potato beetle, small caterpillars and beetle larvae. They also eat diamondback moth eggs, larvae and cocoons.
How much they eat: Developing lacewing larvae eat from 100 to 600 aphids per day.
There are 767 recorded species of spiders in the Prairie provinces.
Identification tips: Spiders are not insects, but belong to a different class of animals called arachnids. Spiders have two body regions (insects have three), eight legs (insects have six) and spiders lack antennae and wings.
What they eat: All spiders are predatory. The different species of spiders in the Prairie Provinces prey on a variety of insects, including aphids, moths, flies and beetles.
Editor’s note: Thank you to John Gavloski, entomologist, Manitoba Agriculture for taking time to help with this article and provide photos. Any errors are ours, not John’s.
Tips to maximize your beneficial insect populations
Try these tips to maximize the populations of predators and pollinators in your fields.
- Before making the decision to spray, be sure that pest populations have reached economic thresholds.
- Use selective insecticides, where practical.
- Apply insecticides selectively. Spray only in patches, field edges or in strips where practical. Some insects, such as cutworms, may occur at high levels only in distinct patches.
- Choose insect-resistant crops where possible.
- Crop rotation can prevent some insects from hitting levels that cause economic damage.
- Provide favourable habitat for beneficial insects and pollinators. Keep in mind that some predators need pollen and nectar to survive during adulthood. Minimum or zero tillage may increase populations of some predaceous insects.