Outbreaks of Tomostethus nigritus (Fabricius, 1804) (Hymenoptera, Tenthredinidae) on Fraxinus angustifolia ‘Raywood’ in Belgium

By

Verheyde, Fons
Sioen, Geert

Type

Article

Date of Publication

2019

Original Publication

Journal of Hymenoptera research

Volume

72

Pages

67--81

Subjects

Ash , gregariousness , Migration , Phenology , sawfly , urban

Contributed by

Pensoft Publishers

Language

English

Published by

Washington, D.C International Society of Hymenopterists

Identifiers

DOI: https://doi.org/10.3897/jhr.72.38284

 

Abstract

In Western Europe the ash sawfly Tomostethus nigritus is known to occur at low densities on Fraxinus excelsior and is uncommonly reported as a pest species. However, we show here that outbreaks can occur on non-endemic trees such as F. angustifolia, and that the species is able to spread quickly using city infrastructure. At the visited localities near the city of Ghent, foliage of Fraxinus angustifolia ‘Raywood’ emerged approximately one month earlier than on F. excelsior. At the same time, changed climatic conditions in the last decade, i.e. higher temperatures in March, caused adults to emerge earlier. Synchronicity of the potential hosts and T. nigritus may therefore have altered, playing a crucial role in population dynamics. Future research should aim to confirm if the species dramatically declines in numbers after reaching its peak population level, an effect which was observed in previous studies, but for which there is still no satisfactory explanation.