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United States Department of Agriculture

Agricultural Research Service

Research Project: Biological Control of Exotic Weeds in California

Location: Exotic and Invasive Weeds Research

2011 Annual Report


1a.Objectives (from AD-416)
Will collect natural enemies of invasive weeds and evaluate host specificity under quarantine conditions. Will conduct field monitoring of released weed biological control agents. Will conduct research on revegetation of native species in riparian habitats such as Fall River, California.


1b.Approach (from AD-416)
New Natural enemies of weeds such as Eurasian watermilfoil, Arundo & Yellow starthistle will be identified and collected through foreign exploration in countries of origin. For most of the target weeds of interest this will be done working with cooperators at USDA-ARS overseas laboratories, in Europe and China. Following location and proper taxonomic assessment, colonies of these beneficial natural enemies will be established and held under quarantine conditions. Environmental assessments will be written to support requests for field release of these natural enemies by ARS scientists. Once approved by USDA-APHIS & other regulatory groups, these agents will be field released and monitored to determine their establishment and impact on both target and non-target plants. A combination of field & laboratory experiments will be used to identify methods of establishing native species in areas where invasive weeds have been eliminated. The initial focus will be on seed physiology production & dispersal, & artificial seeding of beneficial species.


3.Progress Report

ARS scientists in Albany, CA worked cooperatively with the Bureau of Land Management to continue studies on the safety and efficacy of several new biological control agents of invasive thistles, brooms and Cape-ivy. Field assessments were conducted on Bull thistle plants across Northern California where a seed feeding insect was release by CDFA. Heads were collected in the spring of 2011 and are now in the process of being dissected to determine infestation level and impact on seed head viability. A new colony of broom infesting psyllids was established with the aid of the USDA-ARS European Biological Control Laboratory in Montpellier, France. In parallel with the collection and quarantine import of these psyllids, new broom seedlings were established and raised to a six month growth stage. Challenge tests are now being organized to determine the feeding impacts of different densities of psyllids upon these broom plants. These studies will aid in determining whether the psyllids warrant further host specificity testing and potential introduction into North America to aid in French Broom control in California. Research also continued on assessing the host specificity of Cape-ivy natural enemies under quarantine conditions. Initial host-specificity testing showed that two different natural enemies of Cape-ivy, both a fly and a moth, were very specific to Cape-ivy when given a choice between several native plants and the target weed. These data were presented to the USDA-APHIS Technical Advisory Group who were pleased with the results, however, who also suggested an additional 6 potential rare and endangered plant species that they required to be tested. With assistance from various state, federal and local agencies and groups, ARS scientists in Albany, CA have acquired these plants and are now over half-way completed in conducting the required tests. To date, no non-target plants have been impacted by the proposed biological control agents, suggesting that the selected natural enemies will be appropriate to aid in Cape-ivy control. A new up-dated petition to USDA-APHIS will be developed during the winter of FY2012, with the potential to make open field releases of these new biological control agents in the spring/summer of the same year.


Last Modified: 9/1/2014
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