Investigations on the occurrence of wheat bugs (Scutelleridae, Pentatomidae; Heteroptera) in organic farming of Eastern Austria

Summary in the original language of the document

Wheat bugs, an umbrella term for a set of different species, damage wheat by sucking on semi-ripe grains. The proteolytic enzyme inserted with the saliva destroys the gluten. If more than 1.5 – 2% of the grains are infected, the ground wheat loses its baking quality. In 2003, for the first time since the fifties, a significant occurrence of wheat bugs was recorded in Eastern Austria. Since in organic farming no insecticides are available for direct control, the farmers were advised to grow quality wheat at the greatest possible distance to fallows, windbreaks and other uncultivated areas. To clarify their significance for the wheat bug occurrence, a diploma thesis was performed in the year 2004. The sampling sites were situated in Burgenland, Eastern Austria. The spatial and temporal distribution of the bugs (Scutelleridae, Pentatomidae) was evaluated by hand-searching the ground litter and by sampling with enclosures, sweep net and visual observations in windbreaks, forest edges, field margins, grasslands, fallows and winter–wheat fields (1, 10 and 60 meters from the field edge) and sporadically also in other crops (lucerne, barley, rye and spelt). As a total, 368 individuals from 22 species of bugs were collected. 316 individuals belonged to potentially harmful 10 wheat bug species, Eurygaster maura (67%), Aelia acuminata (16%) and E. austriaca (4%) being most abundant. The sweep net was the most efficient sampling method. The earliest wheat bugs occurred directly in the wheat fields. During the growing season, the species E. maura, A. acuminata und E. austriaca were found almost entirely in winter-wheat fields, whereas in the uncultivated habitats other species occurred. Our data do not suggest that landscape elements as well as fallows enhance wheat bug infestations. The wheat bug infestation of wheat fields might be influenced mainly by the weather conditions in spring and summer. After having compared the climatic conditions of 2003 with the “wheat bug years” 1953 and 1954, we suggest that the recent outbreak of wheat bugs might have been due to the significantly above average temperatures in the years 2000 to 2003.