Role of European earwigs in orchards
(Continued from last month)
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.
In the first two years of this project, laboratory and field trial experiments were done to assess the effects of acetamaprid, thiacloprid, abamectin and spirodiclofen on earwig survival, growth, population increase and fecundity (breeding rate).
The results suggest that an occasional application of acetamaprid or thiacloprid to control early-season pests are unlikely to have long-term effects on earwig populations if earwig numbers are already high in the orchard and the application is made in response to pest thresholds.
Field experiments in UK and European orchards have indicated that thiacloprid, indoxacarb, chlorpyrifos and spinosad have harmful effects on earwigs and could be responsible for the low populations of these important predators in some orchards.
As expected European earwig numbers found in chlorpyrifos treated trees declined over time.
Males were not affected by either program, but female and nymph numbers were significantly higher in the earwig-safe program. One or two sprays of harmful products were enough to have a detrimental effect.
Results
These results indicate that a wide range of insecticides and miticides, with some deemed as IPM friendly, may have a detrimental effect on females and nymphs over the longer term.
Earwigs may be a subtle IPM beneficial, but if these products have a detrimental effect on earwigs, what indirect effect do they have on other beneficials?
Building up earwig populations in orchards by selective use of crop-protection products will increase natural control of many major orchard pests but allow occasional sprays of more earwig-harmful products when they are needed to control early-spring or sporadic pests.
See this in Tree Fruit June 2016
