Science into practice: Earwigs -- apple friends or foes?

Previous studies have shown that the common earwig is present in large numbers in many orchards and in windbreak trees.

The insects are nocturnal so numbers can be underestimated, and where artificial refuges are put in orchard trees a large amount of earwigs use them during the day as shelter sites. Releasing earwigs into pear trees significantly reduced numbers of pear sucker and other research suggests earwigs are predators for woolly apple aphid.

HDC project TF 185 examined what earwigs were eating in apple orchards from May until September as a prerequisite for assessing their biocontrol potential. More needs to be known about earwig feeding habits before they can be used in integrated pest management in orchards.

DNA tests on the contents of the guts of earwigs collected in orchards proved to be a much more accurate method than the previous one, where identifiable remains were assessed visually following gut dissections.

A major constituent of the earwig diet throughout the season was algae and fungi associated with lichens. Rosy apple aphids were consumed in June when aphid populations are at their highest. During the study there was also some evidence that earwigs consume apple leaf midge. It was considered that the lichen and fungal material in the earwig gut masked the presence of insect DNA so additional studies are required before firm recommendations can be made.

There was no evidence to suggest that earwigs were causing damage to trees or fruit as no apple DNA was found. Providing refuges for earwigs in orchards may increase biocontrol of pests and should have no deleterious effect on dessert apple quality.

 


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