Phyllopertha horticola (Coleoptera: Scarabaeidae) larvae in eastern Austrian mountainous grasslands and the associated damage risk related to soil, topography and management

Patrick Hann,Bernhard Kromp,Katharina F Wechselberger,Claus Trska,Josef Eitzinger

doi:10.1186/s40064-015-0918-6

Patrick Hann, Bernhard Kromp + Show 3 more

Open Access

https://doi.org/10.1186/s40064-015-0918-6

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Abstract

The soil-dwelling larvae of several Scarabaeidae species (white grubs), like the cockchafer (Melolontha melolontha) and the garden chafer (Phyllopertha horticola), are serious pests in European cultivated grassland, reducing grass yield and destroying the turf by root-feeding. Nevertheless, the factors responsible for the development of large grub populations and the associated damage risk are poorly understood. The objectives of the study were to survey grub densities in grassland sites with different damage histories and find correlations with environmental and management variables. Data on grub densities were collected at 10 farms in the eastern Austrian Alps in September and October 2011. At each farm, one recently damaged site (high risk) and one site at which grub damage had never been observed by the farmers (undamaged site = low risk; each site: 500 m2) were sampled. All sites were dominated by P. horticola (99% of 1,422 collected individuals; maximum density 303 grubs/m2), which indicates that grub damage there is mainly caused by that species. Recently damaged sites tended to higher grub densities than undamaged sites. However, 3 out of 10 undamaged sites harbored high grub populations as well. Humus content together with the depth of the A-horizon significantly explained 38% of P. horticola grub density variance, with highest densities in deeper humus-rich soils. The risk of grub damage was positively connected to the humus content and negatively related to the cutting frequency. For the investigated mountainous grassland sites, these results suggest an important role of humus for the development of high grub densities and an effect of management intensity on grub damage.

Highlights

White grubs, the soil-dwelling larvae of Scarabeidae species, cause severe damage to European cultivated grassland (Keller and Zimmermann 2005, Jackson and Klein 2006)
County Chambers all over Austria, a cumulated area of 14,800 ha of white grub damage were recorded for the investigation period from 2000 to 2006 (Grünbacher et al 2007, Hann et al 2008)
In 2003 and in the sampling year 2011, high proportions of the investigated farms in the region around Fischbach were affected by grub damage (2003: 67% of all investigated farms, 9 farms in total; 2011: 56%, Figure 2). Both years were characterized by comparatively high mean temperatures and low precipitation sums during the adult flight and main larval feeding period of P. horticola (May – September)

Summary

Introduction

The soil-dwelling larvae of Scarabeidae species, cause severe damage to European cultivated grassland (Keller and Zimmermann 2005, Jackson and Klein 2006). Based on a nationwide survey conducted in 2000, Strasser (2004a) forecasted increasing damage caused by Scarabaeidae larvae in several Austrian regions. The Scarabeidae (Coleoptera) species, mainly responsible for grub damage in Austrian alpine grasslands, are the cockchafers (Melolontha melolontha and M. hippocastani), the garden chafer (Phyllopertha horticola) and, to a lesser degree, the June beetle (Amphimallon solstitiale; Pötsch et al 1997, Traugott 2003, Strasser 2004a, Keller and Zimmermann 2005). The survey results of Strasser (2004a) indicated that M. melolontha and P. horticola cause increasing damage in

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