Distinguishing Friends From Enemies: Four Fabulous Insects You Want Visiting Your Orchards

This is always my favourite time of the year to scout apples because of the abundance of beneficial insects buzzing around the orchards. As pest management specialists, we always warn growers about the evil pests lurking around orchards, but all too often we forget to talk about the insect super-heroes that defend our crops against pests. Beneficial insect populations are thriving in well-managed apple orchards munching away on aphids, mites, and an assortment of other pests. There are way too many beneficial insects that are present in apple orchards to mention in this article, so I have decided to focus on the "Fabulous Four": lacewings (Family Chrysopidae), Orius spp, lady beetles, and the aphid midge (Aphidoletes aphidimyza).

Lacewings

Lacewings are one of the most common beneficial insects we are currently seeing in apple orchards. The green lacewing (Chryoserla carnea) is the most common lacewing found in apple orchards in southern Ontario. Adult C. carnea are 7-10 mm long and are pale green with a creamy stripe running down their back, and lace-like wings. The adults feed mainly on aphid honeydew and on nectar and other plant fluids. The females mate and lay eggs individually on long string-like threads. Larvae, sometimes referred to as "aphid lions" or "aphid wolves", have hooked, incurved, or sickle-like jaws. (Fig 1). Larvae are voracious predators of aphids, small caterpillars, leafhoppers, thrips, eggs, mites and sometimes each other.

Fig. 1 Lacewing larvae

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Orius spp.

Although there are several different species of Orius that can be found in apple orchards, Orius insidiosus (Say) is the most common species. Adults (Fig 2.) and nymphs prey upon aphids, mites, leafhopper nymphs, and small caterpillars. These insects hold their prey with their front legs and insert their beak into the host and suck out the juices of the prey. Nymphs and adults have been reported to consume 30 or more spider mites per day.

Fig.2 Adult Orius insidiosus

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Lady beetles

Lady beetles are oval, convex insects; typically with bright coloration. Larvae are often described as "alligator-like". There are several species of lady beetles present in apple orchards. The multi-coloured Asian lady beetle, Harmonia axyridis (Pallas) or MALB is by far the most common species found in Ontario apple orchards.

Multi-coloured Asian ladybird beetle adults have a variety of different patterns on their wing covers, but they can easily be distinguished from other ladybugs by the presence of the black M on their pronotum (Fig. 3). MALB larvae and adults are predaceous on aphids and other soft bodied insects and larvae may consume an average of 23.3 aphids per day, while adults may consume 15 to 65 aphids per day.

Fig 3. Multi-coloured Asian lady bird beetle adult (note black M on pronotum)
(Source: Cornell University)

Aphidoletes aphidimyza-aphid midge

The aphid midge Aphidoletes aphidimyza is one of the prevalent but least recognized beneficial insect found in apple orchards. The larvae are small orange maggots (2-3 mm in size) that are often found feeding in terminals infested with aphids. The larvae (Fig 4.) paralyze aphids by attacking their leg joints, and then suck the aphid dry leaving a blackened collapsed aphid on the surface of the leaf. The larvae drop to the soil and pupate. The adults that emerge are small (2-3 mm) mosquito like flies with long dangling legs and antennae. The adults feed on honeydew and are rarely seen in orchards. Aphid midges attack more than 60 species of aphids, and are a voracious predator.

Fig. 4 Aphidoletes aphidimyza larvae
(Source: Cornell University)

Related Links

• Aphidoletes aphidimyza, Cornell University
• Multicolored Asian Lady Beetle, Cornell University

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