Brachycaudus divaricatae Shaposhnikov has spread in many European countries over the last decades, where it causes intensive damage to Prunus cerasifera. Forty P. cerasifera trees were monitored in 2013 at Dārziņi, on the outskirts of Riga city (Latvia), to obtain data on seasonal dynamics of an exotic aphid species, B. divaricatae. Brachycaudus divaricatae was predominant on its only known host plant species, P. cerasifera. Other aphid species were found on monitored trees: Brachycaudus sp., Hyalopterus pruni (Geoffroy) and Rhopalosiphum nymphaeae (L.). The target species, B. divaricatae was the most abundant, followed by H. pruni, but only B. divaricatae reached the highest infestation level. The latest date of registered B. divaricatae colonies was 31 October 2013. Many predatory arthropods belonging to Acari, Araneae, Coleoptera, Diptera, Hymenoptera, and Neuroptera were registered in B. divaricatae colonies. The most abundant predators were dipteran larvae from the families Cecidomyiidae and Syrphidae. Predatory dipterans most abundant were only at the beginning of the season (June). Later in the season, the number of spiders increased in aphid colonies, and of 365 spiders, 43.8% were members of the Linyphiidae family. Five ant species were caught in B. divaricatae colonies, and Formica cinerea Mayr was the most abundant.
