Earwigs are important generalist predators in apple and pear orchards.
They play a significant and key part in regulating populations of some highly damaging pests including Woolly Apple Aphid and Codling Moth.
Recent research in the UK and Europe has indicated that several commonly used crop-protection products have harmful effects on earwigs in orchards.
Australia has almost one hundred species of earwigs, including several introduced species. Two common species which are often encountered are the native Brown Earwig (Labidura truncata), and the European Earwig (Forficula auricularia).
Like many introduced species, the European Earwig does occur in very large numbers at times and can be seen on flowers at night and under objects and mulch during the day. In these situations it can be a pest and damage some plants and fruit.
Our understanding of European earwigs in orchards may be restricted to their help to control Woolly Apple Aphid. In high numbers, as Earwigs are omnivores (that eat both other insects and plants) they can cause damage to fruits like cherry and stonefruit.
Maintaining a balance
Maintaining a balance between the beneficial aspect and the plant damaging aspect of earwigs has a significant impact on IPM and other pest problems.
Many other pests such as codling moth are significantly reduced, but when earwigs are very low or absent in orchards this contributes to the cause of several pest problems.
European earwigs tend to exist in large groups congregating together. They will generally be more abundant than native earwigs which are usually found as single insects.
Many species of earwig are particularly partial to pollen and can be seen at night moving from flower to flower to feed. As such, they play important roles as pollinators alongside bees, albeit doing the night shift!
European earwigs are also scavengers and feed on all sorts of bits and pieces, including cleaning up the mini-carcasses of dead insects.
They feed at night on a wide range of food types such as organic matter, fruits, ornamental plants, vegetables, flowers, seeds and live and dead insects—including other earwigs and soft bodied insects such as aphids and eggs of insects such as Light Brown Apple Moth, and eggs and larvae of Codling Moth
Role of European earwigs in orchards
The UK Agriculture & Horticulture Development Board (AHDB) has had a number of projects studying the role of European earwigs in orchards and are investigating how to integrate key crop-protection products into pest-management programs without causing harm to earwig populations in the orchard.
AHDB are investigating the lethal and sub-lethal effects of commonly used insecticides on different earwig life stages and different timings during the season.
Continued next month
For more information, see Tree Fruit May 2016
