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United States Department of Agriculture

Agricultural Research Service

Research Project: BIOLOGICAL CONTROL STRATEGIES FOR INVASIVE WEEDS OF SOUTHWESTERN U.S. WATERSHEDS Title: Plant level impacts of the arundo scale (Rhizaspidiotus donacis) on growth and eco-physiology of the invasive giant reed

Authors
item Racelis, Alexis
item Moran, Patrick
item Yang, Chenghai
item Goolsby, John

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 10, 2011
Publication Date: August 12, 2011
Citation: Racelis, A.E., Moran, P.J., Yang, C., Goolsby, J. 2011. Plant level impacts of the arundo scale (Rhizaspidiotus donacis) on growth and eco-physiology of the invasive giant reed. Meeting Abstract. CDROM.

Technical Abstract: The sap-feeding armored arundo scale (Rhizaspidiotus donacis) has been permitted for use as a biological control agent for giant reed (Arundo donax L.), a non-native, highly invasive woody grass that infests waterways and riparian areas of the southwestern US and Mexico. We use a nested factorial design within a controlled greenhouse setting to (1) test the hypothesis that pressure from natural enemies can interrupt the net primary production of giant reed by disrupting water and nutrient transport and detrimentally affecting the photosynthetic ability of the plant and (2) build a predictive model of the density dependant impacts of the arundo scale on plant growth to inform a biological control program. Different densities of the immature stages of two distinct genotypes of the arundo scale are administered to individually-potted ramets of the same genotype of the target weed. Growth parameters of plant such as shoot height and number of nodes, number of shoots, number and length of side shoots are measured monthly for six months, or after one generation of the scale. Insect-induced plant physiological stress is estimated with monthly measurements of light reflectance using a spectroradiometer, and by analyzing differences in leaf gas exchange among the different treatments at the end of the experiment. At six months, all plants are destructively sampled to count the density of mature scale adults and to extrapolate biomass accumulation of the test plants. Initial results suggest a scale density-dependent effect on both plant biomass and water use efficiency. Potted plants that have a high administered density of immature scale tend to have a slower rate of growth than control plants with no insects. If this trend continues, this biological control agent may prove to be an effective tool to curb the negative ecological and social impacts of this weed. These results may help inform an inundative approach to weed biological control.

Last Modified: 12/19/2014
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