Walking Velocity and Estimated Distance of the Armored Scale Crawler Rhizaspidiotus donacis, a Biological Control Agent for Arundo donax.

Arundo scale, Rhizaspidiotus donacis (Leonardi) (Hemiptera: Diaspididae), is an armored scale biological control agent established on the invasive weed, Arundo donax L. (Poaceae; Arundinoideae) at several locations along the Rio Grande in Texas (Goolsby et. al. 2009, Moran and Goolsby 2010, Goolsby et al. 2011, Villarreal et al. 2016). The arundo scale is having significant impact on the target weed in areas where it established (Goolsby and Moran 2019), and no non-target plant use was observed (Goolsby et al. 2020). Armored scale crawlers usually live for less than a day and settle within 1 m of their sessile mother (Beardsley and Gonzalez 1975). Their low level of dispersion led to biological studies of the arundo scale in quarantine before release to quantify aspects of its biology that influenced dispersal. We measured walking velocity, estimated the potential distance a crawler could travel during a 12-hour period, and variations of the attributes for crawlers that emerged over time from different geographical accessions. The information was used to prioritize populations for release at field sites or nearby rearing facility. Three accessions of R. donacis crawlers from France, Italy, and Greece were evaluated (Table 1). Crawlers of each accession were isolated as individuals in gelatin capsules on Monday, Wednesday, and Friday mornings and kept for observation in the laboratory at 23ºC and 50% relative humidity. Crawlers in gelatin capsules were observed with the aid of a dissecting microscope (Leica MZ-16). Distances walked were measured using a stage micrometer during 10-second periods. [ABSTRACT FROM AUTHOR]