There are literally hordes of unpaid workers in your field. They are the quiet, unheralded beneficial insects that work tirelessly to control crop insect pests for you. If it wasn’t for them, we would have poorer crops to harvest in the fall. There are legions of them out there and they are the unsung heroes that keep insects and other pests under control.
Not only are beneficial insects controlling the “bad” insects, they perform other, vital, tasks. Insects are busy pollinating the crops, eating other insects, eating weeds and weed seeds, decomposing stubble and plant residues, freeing up nutrients for the next crop, and improving soil. The destructive ones feed on crops, livestock and stored grains.
There are 10 large groups of insects that help control pest species. The most important of these are the true bugs, lacewings, ground beetles, flies and wasps. In the true bugs, the names tell the story. Pirate bugs, ambush bugs, assassin bugs and stink bugs. They attack and suck out the juices of aphids and other problem insects. Damsel bugs are true bugs and they are important predators of diamondback moth larvae. In studies, one damsel bugs ate 131 eggs or 95 larvae in a 24 hour period. This was in a greenhouse study. In the field it wouldn’t be as high but the consumption numbers are impressive.
These beneficial insects work for field crops in several ways. The insects may merely hunt and eat the adult pests. They also lay eggs in problem insects. These eggs hatch and eat their way out of their host, killing it and preventing it from making more problem insects.
Ground beetles are a large group of insects that help out in the field. They are mostly nocturnal, being active at night, and will attack almost anything they can overpower. Different ground beetles will eat cutworms, potato beetles, root maggots, diamondback moth larvae, wheat midge larvae and eggs of pest species. Some species of ground beetle feed on weed seeds. One, well known star of biocontrol is the lady beetle. Both the adult and larva of the beetles like to eat aphids.
Not all flies are a problem. Hover flies are the second most important group of pollinators after bees. They are often mistaken as wasps or bees. Larvae of many species prey on aphids, thrips and other, crop feeding insects. The stiletto flies larvae feed off of other insect larvae in the soil such as wireworms and earthworms.
Wasps are important for parasitizing larvae of Bertha armyworm, aphids, cereal leaf beetle and diamondback moths. There are many wasp species that are very good at reducing pest species populations.
If you would be interested in learning more about our beneficial insect partners, Alberta Agriculture is hosting a webinar on beneficial insects with John Gavloski, provincial entomologist with Manitoba Agriculture. It will be held March 20 at 10:00 am. The link to register for this webinar is:
The webinar will also be recorded. However, by attending, you have the added advantage of being able to ask John questions related to his area of expertise.
In agriculture, we tend to concentrate and worry about those factors that have the potential to damage yield potential in our field crops. We also need to get informed about those insects that are working on our behalf. Just counting pests only gives an incomplete picture. With an idea of beneficial insect populations and activity, you can make better decisions on using insecticides when and where they are needed. Avoid the situation where you kill more of your beneficials than the pest species.
– Harry Brook, P.Ag. Crop Specialist