Host weed species of Cassida palaestina Reiche, 1858 (Coleoptera: Chrysomelidae) in Siirt province

This study was conducted to identify the host weed species of Cassida palaestina in Siirt Province and to assess its potential as an herbivorous biological control agent against these weeds. Field surveys were conducted during the 2024–2025 growing seasons at 26 locations in the Siirt city center and Kurtalan district, encompassing agricultural fields, fallow lands, roadsides, and degraded pastures. During the surveys, plant species exhibiting feeding damage by C. palaestina and those hosting its eggs, larvae, pupae, and adults were recorded. Taxonomic experts confirmed the identification of both insect and plant species. The findings revealed that C. palaestina primarily feeds on Silybum marianum (L.) Gaertn. and Notobasis syriaca (L.) Cass., successfully develops, and completes its life cycle on these host plants. Population density was notably higher on N. syriaca. Adult beetles caused irregular feeding holes on the leaves, whereas larvae produced characteristic “windowing” damage by scraping the lower leaf epidermis. High insect densities caused extensive feeding damage to leaf tissues, significantly reducing the photosynthetic area and consequently leading to a marked suppression of vegetative growth in the host plants. This study records S. marianum and N. syriaca for the first time in Türkiye as primary host plants of C. palaestina, while the identification of N. syriaca as a host plant represents the first record worldwide. In conclusion, this study demonstrates that C. palaestina has the potential to serve as an effective biological control agent for weed suppression. However, further studies on its host specificity, population dynamics, and potential effects on non-target organisms are required before it can be safely and effectively used in biological control programs.