Monday, December 11, 2006

Self-, conspecific and interspecific host discrimination of a scelionid egg parasitoid of stink bugs

Ali M. A. Mahmoud, and Un Taek Lim, Andong National University, School of Bioresource Sciences, Andong, South Korea

Abstract To evaluateTrissolcus nigripedius as a potential biological control agent of stink bugs such as Dolycoris baccarum and Piezodorus hybneri which cause damage to soybean crops, self-, conspecific, and interspecific host discrimination were investigated using egg masses of Dolycoris baccarum as host. Females T. nigripedius were able to discriminate hosts previously parasitized by themselves. However, conspecific superparasitism partially occurred in 9 and 21%, and the parasitoid mortality was 4 and 2% after 0 and 24 h interval, respectively. T. nigripedius also could not discriminate eggs previously parasitized by another egg parasitoid. Sex ratio of T. nigripedius emerged from egg masses tested in self-, and conspecific host discrimination was female biased, although the proportion of males increased significantly compared to control where T. nigripedius were allowed to deposit without interruption. Three distinct ovipositional behaviors were observed: drumming, probing, and marking on host eggs. The average time spent on each kind of ovipositional behavior on parasitized and previously parasitized eggs was not different. These results indicate that T. nigripedius discriminate host eggs already parasitized by itself, but they superparasitized conspecifically and interspecifically, and provide basic information for the potential use of this parasitoid as a biological control agent of stink bugs.

Key words: Superparasitism, Multiparasitism, Trissolcus nigripedius, Dolycoris baccarum.

Species 1: Hymenoptera Scelionidae Trissolcus nigripedius
Species 2: Hemiptera Pentatomidae Dolycoris baccarum
Species 3: Hemiptera Pentatomidae Piezodorus hybneri