RISK ASSESSMENT STUDIES OF CLASSICAL BIOLOGICAL CONTROL OF BRAZILIAN PEPPER
Invasive Plant Research Laboratory
2009 Annual Report
1a.Objectives (from AD-416)
To reduce the invasibility and dominance of Brazilian pepper in agricultural and natural areas of the U.S. through the use of biologically based IPM.
1b.Approach (from AD-416)
Conduct foreign explorations to identify and prioritize potential agents for biological control. Testing will be conducted to determine suitability for safe biological control introductions. Suitability will be determined through feeding/oviposition/developmental trials on related plant species available in South America. Priority will be given to species that show a high level of specificity for the target weed and pose minimal risk to desirable plant species.
This project relates to the objective of the inhouse project: Prioritizing and evaluating suitable target species for control; conducting surveys to discover natural enemies; studying the ecology of target species and determining the impact of their suppression on ecosystems; conducting risk analysis of potential biological control organisms; and releasing, establishing, evaluating, and transferring biological control agents against target species. The control of invasive weeds in the regional Everglades system is paramount to maintaining the biodiversity contained within it. Brazilian peppertree (Schinus terebinthifolius Raddi., Anacardiaceae), hereafter BP, is arguably the most damaging invasive plant in the system, having invaded over 280,000 ha in southern Florida alone. Several studies have been completed and several other long term studies have been initiated over this time period (1 October 2008 – 30 September 2009). A common garden experiment to gauge differences among the three BP haplotypes presently found in Florida using 60,000 seeds has been completed. The results show hybrid haplotypes to have advantages over both progenitors for several early life history stages, e.g. seed germination, seedling survival, and seedling biomass. A second field experiment to investigate differences in seed viability using 228,000 BP seeds has also been completed. Preliminary results show that seed viability is affected by both soil burial and light environments. Our team has also completed the first season of a multi-year BP biomass harvesting study to predict reproduction (i.e. number of fruit) from plant allometric measures. We have harvested 65 trees, and have taken measures on 757 branches. We have also set up long term BP demography plots at 5 sites to gauge population dynamics. Multi-year data from the tagged BP individuals within these plots will be used to perform a population viability analysis (PVA). The PVA will calculate the population growth rate, that is, whether the studied populations are declining, static, or growing, along with several other key population characteristics. It is vital to know the present population dynamics of this aggressive invasive before any biocontrol agents have been released so the effect of these agents can be quantified.