Establishment ofHarmonia axyridis on Citrus and Some Data on Its Phenology in Greece

Abstract

In September 1993, a colony ofHarmonia axyridis Pallas (Coleoptera:Coccinellidae) was imported from France into Greece. In 1994, insectary-reared adults were released in 11 citrus orchards in four citrus-growing areas of Greece. Between May 19 and June 8, 1994,H. axyridis was recovered from a total of seven localities in three of these areas. This species was established on orange, mandarin and sour orange trees heavily infested withToxoptera aurantii, Aphis spiraecola andA. gossypii; its absence from the remaining four localities may have been the result of low prey densities. Twenty-three days after the initial releases,H. axyridis larvae comprised 57.9% and 83.3%, respectively, of the aphidophagous coccinellid larval populations in two localities (on Chios Island). In samples taken at Leonidion 43 days after the introduction release, both adult and larval populations ofH. axyridis represented approximately one-third of aphidophagous coccinellid adults and larvae found, whereas the indigenousAdalia bipunctata comprised about one-half of the population. In cages placed outside the Athens laboratory,H. axyridis completed four overlapping generations annually; average longevities of 56.2, 66.8, 78.9 and 102.2 days, respectively, were recorded for the successive generations. Adults of the 3rd and 4th generations overwintered, giving rise to the following year’s 1st generation. Oviposition began in April and emergence of 1st generation adults occurred in mid-May. The egg-laying activity of the females throughout the warm period of the year indicates thatH. axyridis does not diapause in summer. From December until March, small aggregations (2-4 individuals) were observed within the cages at protected sites.