Effect of Achillea millefolium Strips and Essential Oil on the European Apple Sawfly, Hoplocampa testudinea (Hymenoptera: Tenthredinidea)

Abstract

The European apple sawfly Hoplocampa testudinea (Klug) (Hymenoptera: Tenthredinidae) is a pest in numerous apple orchards in eastern North America. In Quebec, Canada, the European apple sawfly can damage up to 14% of apples and growers use phosphate insecticide during the petal fall stage to control the pest. Since the insecticide is toxic for beneficial insects, we established flower strips of Achillea millefolium L. (Asterales: Asteraceae) to interfere with the oviposition of the insect as an alternative. Populations of European apple sawfly adults were significantly reduced in areas close to flower strips compared to unmanaged areas (natural groundcover). In order to understand the mechanism of the flower strip effect, we tested the repellent effect of A. millefolium essential oil on populations of H. testudinea. Twenty flowers per apple tree were sprayed during full bloom, the oviposition period of the pest. Sprayed and control flowers were then collected and dissected to note the presence of oviposition scars and eggs of the European apple sawfly. Significantly less scars and eggs were observed on sprayed flowers than on control flowers, which means that A. millefolium had a repellent effect on the insect.