Chrysolina fastuosa (Coleoptera: Chrysomelidae) a biological control agent or a possible pest?

A poorly known chrysomelid beetle, Chrysolina fastuosa (Scopoli) has been found in a strikingly great number on black horehound (Ballota nigra L.), a soft caulescent plant belonging to the Lamiaceae family. B. nigra can be found from April to August commonly on roadsides, along walls or at the border of gardens and orchards in Hungary and continental Europe. It can be called a minor weed. The glistering tiny adults that feed voraciously on leaves cause apparently significant damage. The subsequent investigation, which focuses on the number of feeding individuals and the loss of plant tissue, showed 1–24 beetles on a plant and the consumed leave surface which amounted to 8–94%. The repeated damage assessment, a week later showed a significantly unimportant increase in the number of individuals but a significant 20–31% increase in the plant surface loss. According to the literature, Ch. fastuosa has been found in association with other Labiatae plants such as Galeopsis pubescens Besser, Lamium album L. and Urtica dioica L. (Urticaceae). Thus, considering its efficiency mentioned above, it could be used to augment and maintain its populations as a biological control agent for these weeds. However, taking into consideration the growing importance of the production of medicinal plants among which Lamiaceae species are numerous, Ch. fastuosa can cause damage that cannot be neglected.