Is the European earwig a beneficial insect or a pest?
It’s actually both!
The cosmopolitan European earwig, Forficula auricularia, can be a beneficial, natural enemy of pests in agricultural systems, particularly in orchards where they feed on aphids and moth larvae.
But in Australia, the European earwig is an introduced, invasive species and pest of the grains industry.
Our team has recently tested the susceptibility of 7 host plants against different growth stages of the European earwig to determine which crops are most at risk of damage.
How was this research undertaken?
cesar research scientist, Lisa Kirkland, performed microcosm trials that tested European earwig feeding damage to 7 host plants – lucerne, canola, lentils, lupins, chickpeas, wheat, and oat – at two early growth stages.
Immature, second and fourth instar European earwig were tested along with summer adults and winter adults to allow researchers to determine the potential risk to grain crops sown at different times of the year, and also the feeding voracity of earwigs at different stages of their development.
What did our researchers find?
All 7 crop types experienced some level of feeding damage from the European earwig, with the younger of the two growth stages receiving the most damage, in most cases.
Lucerne and canola were found to be the most susceptible to European earwig feeding.
In fact, lucerne was found to be vulnerable at both growth stages to all 4 of the earwig life stages tested.
Lentils and lupins were also susceptible to this pest but not to the extent that lucerne and canola were.
Chickpeas, wheat and oats only experienced mild damage from the European earwig.
The research also showed that immature stages of European earwig can cause as much damage, if not more damage than the adult stages, with the fourth instar stage causing the most damage on average to all the crop seedlings tested, followed by the winter adults.
What does this mean for growers?
Monitoring for the European earwig during crop establishment is important as winter adults will be around and producing nymphs at this time of the year, threatening crops in the early seedling stage of growth.
Canola and lucerne in particular, should be monitored carefully during establishment, particularly along crop edges.
Fortunately, numbers of the most voracious fourth instar earwig on grain farms don’t peak until spring, by which stage, autumn sown crops are vigorous and unlikely to be susceptible to significant damage.
The European earwig is nocturnal so monitoring should be done at night with a torch. Hessian sacks, tiles or cardboard rolls, can be used as shelter traps to monitor for the earwig as they create a perfect environment for the pest.
Damage typically results in irregular holes in leaves or leaves with a shredded appearance.
The European earwig may be mistaken with the native common brown earwig. For help with European earwig identification, watch our PestBites episode or contact our PestFacts south-eastern team (firstname.lastname@example.org).
For more information on the European earwig see our PestNote.
This work was made possible with financial support from the Grains Research & Development Corporation (CSE00059). Our project partners are CSIRO, the University of Melbourne, NSW DPI, SARDI and WA DPIRD.
Thanks to Lisa Kirkland for reviewing this article.