Unmown groundcover conserves adult populations of the predatory ground beetle Chlaenius micans (Coleoptera: Carabidae) in commercial apple orchards

Abstract

To improve the success of integrated pest management in commercial apple orchards, I investigated whether the use of unmown white clover groundcover would enhance the numbers of a predatory ground beetle, Chlaenius micans (Fabricius), relative to mowing. From 2009 to 2011, narrow-spectrum insecticides were sprayed in one apple orchard and broad-spectrum insecticides in another in Akita Prefecture, northern Japan. Half of each orchard was plowed and sown to white clover in mid-April 2009; subsequently, these plots were not mowed and herbicides were not applied. The other half of each orchard was mowed every 3 weeks from mid-May to late August each year, and herbicides were sprayed around trees in mid-June. Significantly more adult Ch. micans were captured in pitfall traps in the unmown clover plots than in the mown plots. Thus, the retention of unmown groundcover increased the populations of adult Ch. micans in apple orchards.