Parasitoid complex and parasitism rates of the horse chestnut leafminer, Cameraria ohridella (Lepidoptera: Gracillariidae) in the Czech Republic, Slovakia and Slovenia

Lubomír Volter,Marc Kenis

doi:10.14411/eje.2006.049

Abstract

The horse chestnut leaf miner, Cameraria ohridella Deschka & Dimi¸ , is a species of unknown origin that recently invaded most of Europe, causing serious damage to horse chestnut trees, Aesculus hippocastanum. Parasitism was studied over a period of three years in the region of Plze�� in the Czech Republic. Additional collections were made in Slovakia and Slovenia. The parasitoid complex, dominated by polyphagous idiobiont parasitoids of the family Eulophidae, is similar to that found in other studies in Europe. Minotetrastichus frontalis (Nees) was the most abundant parasitoid found, except in Slovakia where Pediobius saulius (Walker) dominated. One parasitoid species, the eulophid Cirrospilus diallus (Walker) was recorded for the first time from C. ohridella. A new method is proposed to calculate stage-specific and total parasitism rates. Parasitism rates of spinning larvae and pupae were higher than of feeding larvae; however, total parasitism was low. We estimated that between 1% and 17% of moths died from parasitism during the larval and pupal stages whereas the rate of mortality caused by other factors varied from 7% to 62%, depending on the locality, year and generation. The proposed method for calculating total parasitism, based on the integration of stage-specific parasitism rates, which takes into account the mortality not directly attributed to parasitism, is discussed and compared with other methods commonly used in studies on C. ohridella.

Highlights

In the last 30 years, several alien leaf mining moths, mainly of the family Gracillariidae, invaded Central Europe (Šefrová, 1998, 2002a, b, c)
Ten parasitoid species were obtained in the Czech Republic, with the most abundant parasitoid species being Minotetrastichus frontalis, accounting for nearly 40% of the parasitized mines, and Pnigalio agraules, which was found in 19% of the parasitized mines
P. saulius was present in Slovenia but was never reared from the numerous samples collected in the Czech Republic

Summary

Introduction

In the last 30 years, several alien leaf mining moths, mainly of the family Gracillariidae, invaded Central Europe (Šefrová, 1998, 2002a, b, c). The impact of these native parasitoids on host populations strongly depends on host species (Godfray et al, 1995; Gibogini et al, 1996; Urbaneja et al, 2000) One of these invasive species is the horse chestnut leaf miner, Cameraria ohridella, Deschka & Dimiü (Lepidoptera: Gracillariidae), a moth of unknown origin that was first observed in Macedonia in 1984. (3) Most parasitoids that attack an alien leaf mining moth, are polyphagous and idiobionts, i.e. host development ceases when parasitised They tend to attack mainly the late developmental stages (spinning larvae and pupae) and collections made during the feeding stages will largely underestimate parasitism. Previous studies on parasitism of C. ohridella have calculated parasitism rates based on emergence data (e.g. Grabenweger & Lethmayer, 1999; Hellrigl, 2001; Grabenweger, 2003) or, when dissections of single mines were made, parasitism rates were obtained by dividing the number of parasitised mines by the total number of mines (e.g. Freise et al, 2002; Grabenweger et al, 2005; Lupi, 2005)

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