Most insects observed in the field are either beneficial or benign. Relatively few insects cause damage to crops.
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 that feed on mite eggs. Parasitoids include various small wasp species and certain types of flies.
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Pollinators provide benefits in strawberry, raspberry and chokecherry crops. Insect pollination can result in a better yield through increased berry size.
Predatory and parasitic insects are primary pest controls in non-outbreak situations, and killing them 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. Insecticides kill both predators and pollinators. Here are some beneficial bugs.
Ladybugs
The adults are the familiar ladybugs but the larvae are unusual in appearance and are even more voracious than the adults.
Ladybug 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 up to one year. There are one or two generations per year, depending on the species.
Hover flies
The adults resemble small bees or wasps but can be distinguished by their hovering behaviour. The larvae are green or pink and are tapered toward 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 good pollinators.
Green lacewings
The adults are green, with net-veined wings and gold eyes. The larvae are alligator-like in appearance, similar to ladybug, 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. The larvae feed on a variety of prey, including aphids, thrips, mites, eggs of many insects including leafhoppers and moths, plus small caterpillars and beetle larvae.
Bees
Bees are also efficient pollinators. In addition to honeybees, there are a number of species that visit and pollinate berry crop flowers.
For strawberries, the presence of pollinators can boost berry weight up to 20 percent. They also aid in proper berry formation.
Lack of insect pollination can result in apical seediness in strawberries, which is sometimes confused with tarnished plant bug damage.
