Effects of harvest on survival and dispersal of insect predators in hay lucerne

The short-term effects of harvesting on survival and dispersal of insect pr edators in hay lucerne (Medicago saliva L.) were investigated in a commerci al crop in Australia. Adults of two coleopterans, transverse ladybird beetl e (Coccinella transversalis Fabricius Coccinellidae) and pollen beetle (Dic ranolaius bellulus (Guerin-Meneville) Melyridae), and one heteropteran, spi ned predatory shield bug (Oechalia schellembergii (Guerin-Meneville) Pentat omidae), were marked and released into lucerne strips immediately before th ey were cut for hay. Vacuum sampling of the stubble immediately after harve st showed that proportional mortalities were 0.16, 0.00 and 0.07 respective ly. Proportions of the released individuals that were recovered alive were 0.66 for C. transversalis, 0.45 for O. schellembergii and 0.02 for D, bellu lus. The proportion of predators that were not recaptured from release area s was greatest for D, bellulus (0.80). To assess dispersal after harvest, 1 2 strips of lucerne were left uncut within the field in which the marked in sects had been released. Intensive sweep-net sampling of these strips caugh t marked survivors of all three predators. The numbers of insects caught in strips declined with increasing distance from the release point. Many inse ct predators, therefore, survived harvesting and, if uncut refuge strips ar e provided, the within-field community of biological control agents is larg ely preserved.The short-term effects of harvesting on survival and dispersa l of insect predators in hay lucerne (Medicago saliva L.) were investigated in a commercial crop in Australia. Adults of two coleopterans, transverse ladybird beetle (Coccinella transversalis Fabricius Coccinellidae) and poll en beetle (Dicranolaius bellulus (Guerin-Meneville) Melyridae), and one het eropteran, spined predatory shield bug (Oechalia schellembergii (Guerin-Men eville) Pentatomidae), were marked and released into lucerne strips immedia tely before they were cut for hay. Vacuum sampling of the stubble immediate ly after harvest showed that proportional mortalities were 0.16, 0.00 and 0 .07 respectively. Proportions of the released individuals that were recover ed alive were 0.66 for C. transversalis, 0.45 for O. schellembergii and 0.0 2 for D, bellulus. The proportion of predators that were not recaptured fro m release areas was greatest for D, bellulus (0.80). To assess dispersal af ter harvest, 12 strips of lucerne were left uncut within the field in which the marked insects had been released. Intensive sweep-net sampling of thes e strips caught marked survivors of all three predators. The numbers of ins ects caught in strips declined with increasing distance from the release po int. Many insect predators, therefore, survived harvesting and, if uncut re fuge strips are provided, the within-field community of biological control agents is largely preserved.