Validity of realized vs. fundamental host range of insects used as biocontrol agents of invasive alien weeds: Eucalyptus weevil (Gonipterus scutellatus) as a test case

摘要

The conservative method of host specificity testing dictates that a potentialudbiological control agent which shows polyphagous behaviour in the laboratory willudbe rejected, even though in a natural situation it may be monophagous or nearly so.udTo distinguish one from the other the performance of eucalyptus weevil,ud(Gonipterus scutellatus) was tested on 14 Eucalyptus and one Syzygium species inudthe laboratory, and the field. The weevil revealed different levels of polyphagy,uddepending on how the host plants were presented; as cut leaves, bouquets orudsleeved-branches; or in choice or no-choice combinations. However, theudfundamental host range was broader than the realized host range. Eucalyptusudsmithii and E. urophylla were the most preferred hosts (contrary to the literature),udwhile E. saligna and Syzygium myrtifolia were immune to feeding and oviposition.udNevertheless, adult feeding and oviposition was more selective in the field, and theudlarvae are less discriminating than the adults. Finally, the weevil is shown to have audnarrow host range within two sections of the subgenus Eucalyptus, sufficientlyudrestricted if it was ever to be considered as a biocontrol agent.