Mass attack of phragmites australis by hyalopterus pruni homoptera aphididae significance of habitat size edge infestation and parasitization
Zoologische Jahrbucher, Abteilung fur Systematik, Okologie und Geographie der Tiere 116(4): 329-334
Abundance of Hyalopterus pruni (Homoptera, Aphididae) was studied using samples from six habitats of common reed (Phragmites australis). H. pruni was 5 times more abundant within the edges of habitats than inside habitats (Table 2). Accordingly, small habitats (with their great edges) had more attacked reed leaves .times. m-2 than large habitats (rs = -0.812, Table 1). Differentiation between thick, protein-rich and thin, protein-poor shoots - within and between habitats -did not contribute to the explanation of the variability of aphid abundance. H. pruni attacked only reed shoots between June and August, the time of strongest growth of comparatively nitrogen-rich shoots, so that host plant quality is presumed to be an important reason of the migration of H. pruni between its secondary host plant P. australis and its primary host plant (Prunus spp.). Hyperparasitoids (6 species) were reared from 80% of the aphid mummies (Table 3). Despite many species of predators and 2 species of primary parasitoids. heavy outbreaks of H. pruni and damage of reed shoots within the "natural monocultures" of P. australis were observed. Heavy outbreaks, conspicuous shoot damage, and the yearly new host plant colonization are effects very similar to the monocultures of cereals with their aphid calamities.