Science Into Practice - Researching earwig decline

Reports that earwigs are declining in some apple and pear orchards have raised concern for pest control and is it thought that this problem could be linked to the use of certain crop-protection products.

The HDC has been funding Project TF 196 at East Malling Research to investigate the lethal and sub-lethal effects of commonly used insecticides on different earwig life stages.

In the first two years, studies were made in the laboratory and on whole trees in orchards to identify products that are harmful to earwigs. Following application to trees at two different timings, thiacloprid and flonicamid treated plots had significantly fewer earwigs than untreated control trees and numbers found in chlorpyrifos treated trees declined over time.

In the final year, conventional spray programmes on two commercial apple farms were compared to "earwig safe" programmes. The latter was based on evidence from previous studies and used safer insecticide alternatives at key earwig life cycle stages.

Refuge bottles were placed in the orchards and night-time assessments of earwig numbers were made in April, June and August. Males were not affected by either programme, but female and nymph numbers were significantly higher in the earwig-safe programme. One or two sprays of harmful products were enough to have a detrimental effect.

Further work is required on the effects of products on survival, behaviour, growth and reproduction, and also to evaluate the effects of different spray timings.

Horticultural Development Company

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