Moran, P.J., Goolsby, J.A., & von Ihering, H. 2008 Preliminary evaluation of the armored scale Rhizaspidiotis donacis (Diaspididae) as a biological control agent of giant reed (Arundo donax).. Proceedings of the XI International Symposium on Scale Insect Studies, Oeiras, Portugal, 24-27 September 2007. ISA Press Lisbon, Portugal 322 pp.

Notes: Biological control is a critical component for management of the giant reed (Arundo donax L.), an exotic invasive weed which grows along the rivers and reservoirs in the Lower Rio Grande Basin river drainage of the USA and Mexico. Giant reed infests over 50,000 hectares in this region, removing valuable water, altering stream flow patterns, impeding river access, and excluding endemic native plants and animals. Exploration in France and Spain identified the armored scale insect Rhizaspidiotus donacis Leonardi as one of several natural enemies that cause substantial damage to this plant and appear to be highly host-specific on giant reed in its native range. Infestation by R. donacis can cause leaf curling and abnormal stem growth. Plant stems and rhizomes shipped from sites near Montpellier, France, and from Barcelona and Huelva, Spain were caged in a quarantine laboratory in Texas, USA. Crawlers emerged from this dead plant material and were collected. Crawlers settled within 24 hours of release onto new giant reed shoots, mostly on leaf collars surrounding the stems. Under constant warm temperatures (27-30°C), white cottony secretions appeared within 4 days of settling, and the first-instar nymphs molted to the second instar within 7-10 days. Adult males emerged within 4-8 weeks after settling. Females molted to the adult stage within this time frame and lived for up La 5 months or more. However, females did not produce a new generation of crawlers under either warm (27-30°C) or cool (l0°C) constant temperature regimes, or under a fluctuating regime (14-27°C) designed to simulate summer conditions in southern coastal France. Several critical issues must be resolved in order to characterize the biology, host specificity and efficacy of R. donacis. Limitations on crawler survival and establishment need to be identified. The environmental factors and population structure (synchronous or asynchronous) necessary for insemination of females by winged males need to be determined. The roles of host plant phenology, temperature, and other factors in controlling crawler production by mated females also need to be clarified.