Spread, mass occurrence and damages of Ophraella communa LeSage, 1986 on Ambrosia artemisiifolia L. in continental Croatia

Based on targeted faunistic surveys, 34 new occurrences of ragweed leaf beetles (Ophraella communa, LeSage) in ten counties of continental Croatia are presented. From mid-July to the end of September 2022, the 34 locations, where ragweed (Ambrosia artemisiifolia L.) regularly occurs, were visually inspected. All developmental stages of the insect were found at all locations during July and August, while only adults were found at all locations in September. At 12 locations, ragweed infestation was estimated to be less than 10%. At 10 locations, damage caused by feeding ranged from 10 to 50%, and at seven locations from 50 to 80%. The mass occurrence of ragweed leaf beetles and complete destruction of common ragweed plants in Croatia was recorded at five monitored locations in four counties. A high level of foliar damage indicates that the species has been well established in the monitored area. The ragweed leaf beetle appears to be spreading rapidly over large areas and is capable of effectively controlling invasive common ragweed. Future work should focus on monitoring the spread, establishment, and impact of this species in Croatia and its inclusion in biological ragweed control measures.