Globose scale or plum lecanium, (Sphaerolecanium prunastri) is a highly specialised plant parasite related to aphids, and whiteflies. Adult females don’t look much like insects at all, as they lack wings and are immobile for much for their lives. Male insects, however, have extra developmental stages and the adults looking with tiny flies with a single pair of wings. Globose scale are native to southern and central Europe, but it geographical range appear to be spreading northwards, possibly in response to climate change. This Spring, a huge population of globose scale was found in Brussels, Belgium, it infested mature ornamental cherry trees (Prunus cerasifera) planted along a street in the centre of the city. This was the first time that Globose scale had been recorded in Belgium and it appears to be the most northerly record in Europe so far. Globose scale feeds mainly on trees from the Prunus group, which includes cherries, plum and peach, but is rarely found on other plants. In southern Europe, population outbreaks can completely encrust branches causing stunting, drying out, dieback, and occasionally plant death. Since Globose scale is now found in Belgium there is a potential risk that it could establish in parts of southern England and have an impact on ornamental and orchard Prunus spp. If you are taking part in the OPAL tree health survey please look out for this insect, especially if you are monitoring a peach, plum or cherry tree.
To find out more read the most recent Observatree blog.