Reproductive biology of Sclerodermus brevicornis, a European parasitoid developing on three species of invasive longhorn beetles

Abstract

Massimo (2017) This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Cerambycidae). Sclerodermus brevicornis attacked all three species, but offspring only developed to maturity on medium and large sized host larvae. Host species influenced the duration of parasitoid development and the number of offspring maturing, both were greatest on A. glabripennis, with up to 373 adult parasitoids emerging from a single host. The sex ratios of S. brevicornis broods were strongly female biased (ca. 9% males). We conclude that S. brevicornis has the potential to be efficiently mass-reared and actively deployed in the biological control of invasive longhorn beetles. Further progress should be encouraged by the successful use of other species of Sclerodermus against beetle pests in China.

Factors Affecting the Reproduction and Mass-Rearing of Sclerodermus brevicornis (Hymenoptera: Bethylidae), a Natural Enemy of Exotic Flat-Faced Longhorn Beetles (Coleoptera: Cerambycidae: Lamiinae)

“…A laboratory rearing system for S. brevicornis was set up in 2011 starting with specimens collected in the north of Italy (45°49′ N, 9°13′ E) where they were found in association with P. h. hilaris [ 84 ]. Subsequent findings in the field allowed the enrichment of the stock culture [ 45 ]. Rearing was carried out in a climate chamber at 23 ± 1 °C, 16L:8D, and RH 60 ± 5%.…”

“…As host size influences the number of offspring produced, medium and large size hosts were chosen (following Lupi et al, [ 45 ]) in order to obtain large numbers of adult wasps and maximize the probability of broods containing adult males as well as females. Larvae were placed individually in plastic jars (5.5 cm diameter × 3.2 cm height) and female wasps (foundresses) added according to the protocol in Lupi et al [ 45 ]. When the host was paralyzed by the foundresses, the lid was micro-perforated with a needle to allow ventilation.…”

“…Biological control has been widely investigated as the priority method for the containment of exotic pests in general and of pests of woody plants in particular, and many studies have considered the potential of both introduced and autochthonous parasitoids to control invasive pests [ 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 ]. Most parasitoids attacking longhorn beetles belong to the Hymenoptera [ 32 , 33 ]; some attack hosts at the eggs stage (species in the families Eulophidae [ 34 ], Encyrtidae [ 35 , 36 , 37 ] and Pteromalidae [ 38 ]) and some attack hosts during the larval stage (species in the families Braconidae [ 39 , 40 , 41 , 42 ], Ichneumonidae [ 42 , 43 ] and Bethylidae [ 44 , 45 ]). Only a minority of this array of parasitoids of exotic longhorn beetles is likely to be effective within biocontrol programs as they must ideally be both suitable for mass production and release and subsequently able to detect and access the target pest inside its galleries [ 41 , 46 ].…”

“…However, following its detection in association with Anoplophora spp. [ 78 ] and with Psacothea hilaris hilaris [ 79 ], a program of research into the biology of Sclerodermus brevicornis has begun to explore its potential for application in biological control programs as well as to better understand the unusual quasi-social life-histories exhibited within the genus [ 45 , 61 , 62 , 63 ]. Here we provide further evaluations of the reproductive performance and mass-rearing potential of Sclerodermus brevicornis .…”

“…The feasibility of large-scale rearing of S. brevicornis on the natural host P. h. hilaris, and on the exotic invasive species A. chinensis and A. glabripennis, was first evaluated by Lupi et al [ 45 ], who showed that it could successfully attack all three species and that rearing was more efficient when large sized host larvae were provided, often generating over 100 offspring per host. However, the trialed beetle hosts are themselves laborious to obtain and rear in the laboratory.…”