Biology and natural enemies of Agrilus fleischeri (Coleoptera: Buprestidae), a newly emerging destructive buprestid pest in Northeast China

Abstract

Agrilus fleischeri Obenberger (Coleoptera: Buprestidae) is an emerging pest of poplar trees in northeast China, and is responsible for poplar mortality throughout its range. Its biology and natural enemies were studied at two field locations from 2013 to 2015 as well as via laboratory experiments. Life history of A. fleischeri was univoltine on exotic Populus nigra var. italica and overwintered as mature larvae in pupal chambers; however, was semivoltine on native Populus davidiana and overwintered as 2nd or 3rd instar larvae in Liaoning Province, China. Adults emerged from late May to mid-August with a peak in early June. Eggs were first discovered in early June and continued to late August. Larvae fed from mid-June to late September of univoltine or from mid-June to the next early September of semivoltine. The sex ratio of adult beetles was approximately 1:1 (M:F). Mean longevities of female and male adults were 34.87±18.70 and 34.33±18.10days, respectively. Mean duration of egg stage was 12.83±1.10days and pupal duration 26.40±1.32days. Mortality in the field was mainly caused by parasitoids; however, pathogens, predators, and host tree resistance were also noted. The egg parasitoids, Oobius spp. attacked 48.0% and 6.48% of A. fleischeri eggs in P. nigra var. italica and P. davidiana, respectively. Polystenus rugosus and Paramblynotus sp. parasitized 0.71% and 52.17% of larvae in P. nigra var. italica respectively. Euderus fleischeri, Polystenus rugosus, and Spathius sp. were found in P. davidiana with parasitism rates of 7.63%, 4.83%, and 0.25% respectively.