Pteromalid fauna (Hymenoptera, Pteromalidae) in oilseed rape (Brassica napus L.) fields in Bulgaria – species composition and perspectives for biological control

Abstract

Parasitoid wasps belonging to the family Pteromalidae are widespread and abundant members of the insect communities in the temperate regions of the world. As many other chalcids do, pteromalids serve as natural enemies of the pests in various crops and play an important role in the biological control of these harmful insects. Here we present the results of a field study in Bulgaria which was focused on the diversity of family Pteromalidae in ten oilseed rape fields. All samples were collected by sweep netting on the border line or inside the crop field. A total of 93 pteromalid specimens belonging to 26 taxa were gathered. The most abundant genus was Mesopolobus – 67% of the sampled pteromalids. The most numerous species in the samples was Mesopolobus morys – a well-known key parasitoid of the cabbage seed weevil, Ceutorhynchus obstrictus, in Europe. One species – Halticoptera patellana, is recorded for the first time in Bulgarian fauna. Clearfield oilseed rape fields had relatively higher parasitoid abundance and richness than the fields treated by conventional technology. In the present work we discuss the overall species composition of Pteromalidae obtained from the studied areas and present our point of view on the perspectives for biological control of oilseed rape pests.

Diversity of parasitoid wasps (Insecta, Hymenoptera) in oilseed rape fields in Serbia

“…Other parasitoid species of these two pests were either not observed or observed in very low numbers. Todorov et al (2022) recently presented a checklist of the pteromalid fauna in Bulgarian oilseed rape fields and recorded 26 taxa, but, interestingly, did not find any Trichomalus species. Parasitoids of the cabbage flea beetle ( P. nemorum ) are represented only by Townesilitus bicolor , while other known species are absent or could not be determined at the species level, but only at the genus level.…”

“… Petrović (2022) compared the parasitoid wasp fauna of the subfamily Aphidiinae from different European countries and found that only the Czech fauna had greater diversity (about 135 species) than the Serbian fauna (121 species), while other countries, such as Germany (109), the United Kingdom (96) and Norway (26), had fewer species, although the Czech fauna may simply be much better studied. To date, only Todorov et al (2022) have published a partial list of oilseed parasitoids for one Balkan country, Bulgaria and only for the family Pteromalidae . However, only two species ( Mesopolobus incultus and M. morys ) are recorded in both Bulgaria and Serbia, with the possible existence of several other taxa of the genera Mesopolobus and Pteromalus that are difficult to identify to species level.…”

“…To the best of our knowledge, there has not been a comprehensive list of parasitoids and hyperparasitoids that occur in oilseed rape fields for this region. Todorov et al (2022) provide a list of parasitoid species found in oilseed rape fields in Bulgaria with comments on perspectives for biological control, but only for the family Pteromalidae . Oilseed rape pests, on the other hand, are relatively well studied in Serbian fields from both taxonomical and traditional chemical management aspects ( Kereši et al 2007 , Sekulić and Kereši 2007 , Štrbac et al 2007 , Mitrović et al 2008 , Milovac et al 2010 , Graora et al 2013 , Milovanović et al 2013 , Graora et al 2015 , Sivčev et al 2015 , Sivčev et al 2016 , Milovac 2016 , Marjanović and Prodanović 2021 ).…”