Beneficial Insects: Pollinators, Predators, and Parasites

Distribution

Beneficial insects are distributed widely in all growing areas. The majority of insects that are observed in the field are either beneficial or benign. Relatively few insects cause damage to crops and the opinion that insects in a field mean nothing but trouble couldn’t be further from the truth. A significant number of insects are predatory on pest insect species. Other insects are parasitic on pest insects and feed on them from within. These predators and parasitoids help to control populations in non-outbreak situations. Predators include ladybugs, lacewings, hover fly larvae, minute pirate bugs, ground beetles, spiders, predatory mites and even thrips, which feed on mite eggs. Parasitoids include various small wasp species and certain types of flies.

Pollinators provide benefits in strawberry, raspberry and chokecherry. Insect pollination in these crops can result in increased yield through increased berry size.

Both predators and pollinators are very susceptible to insecticides.

Predatory and parasitic insects are primary pest controls in non-outbreak situations, and killing them off often results in pest outbreaks, especially mites that are less susceptible to insecticides. Pesticides are necessary tools but should be used only when the economic threshold is surpassed to prevent unnecessary killing of beneficial insects.

Ladybird Beetles or Ladybugs (Coleoptera; Family Coccinelidae)

These insects are effective predators in orchards. The adults are the familiar ladybugs but the larvae are unusual in appearance and are even more voracious than the adults. Larvae are alligator-like in appearance and are black with white, yellow, red or orange markings. They feed primarily on aphids but will also eat other small insects, as well as insect eggs. These insects overwinter as adults and may live for up to one year. There are one or two generations per year, depending upon the species.

Green Lacewings (Neuroptera; Family Chrysopidae)

Adults are green in colour with net veined wings and gold eyes. The larvae are alligator-like in appearance (similar to ladybird larvae), cream coloured with brown markings and sickle-shaped mandibles. These insects overwinter as adults and emerge in early spring to lay eggs. Adults feed only on nectar. There are two or three generations per year. Larvae feed on a variety of prey, including aphids, thrips, mites, eggs of many insects (including leafhoppers and moths), and small caterpillars and beetle larvae.
Hover Flies (Diptera; Family Syrphidae):

Adults resemble small bees or wasps but can be distinguished by their hovering behaviour. The larvae (or maggots) are green or pink in colour and are tapered towards the head. Larvae feed primarily on aphids. These insects overwinter as pupae. If there is abundant food, there can be up to five generations per year. Adults feed on pollen and nectar and are very effective as pollinators.

Bees (Hymenoptera; Family Apidae)

Bees are very efficient pollinators. In addition to honeybees, there are a number of species of wild bees that will visit and pollinate flowers of berry crops. Pollinators are beneficial in strawberry, raspberry and chokecherry. Saskatoon does not benefit from pollinators. In strawberry, the presence of pollinators can result in a yield increase of up to 20% (increased berry weight). They also aid proper berry formation. Lack of insect pollination can result in apical seediness of strawberry, which is sometimes confused with tarnished plant bug damage.

For further information, contact your GO representative.