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ARS Home Southeast Area Fort Lauderdale, Florida Invasive Plant Research Laboratory Research





- Wheeler, Gregory
- Crop Protection & Quarantine (304)

Research Project: **Location:
                            Invasive Plant Research Laboratory** Project Number: 6032-22000-013-113-N
                        
                        Project Type: Non-Funded Cooperative Agreement Start Date: Aug 1, 2023
                        
                        End Date: Oct 1, 2024 **Objective:**
                        
                        The primary purpose of this project is to reduce populations of the aggressive invasive weed, Brazilian peppertree by the development of a newly approved biological control agent. This environmentally safe, cost-effective, and sustainable means of weed control will be accomplished with the approved thrips, Pseudophilothrips ichini. Research will be conducted to examine the impact of the thrips on populations of the target weed.  

Brazilian pepper is one of the most invasive weeds in Florida covering over 280,000 hectares in the peninsula alone. To limit the Brazilian peppertree invasion, public land managers in the state of Florida spend nearly $3 million annually on chemical and mechanical controls. However, these controls are often ineffective or problematic due to the weed’s ability to regrow from cut stumps and the inaccessibility of many remote stands. Because of these difficulties, the lack of effective controls, and their high cost, classical biological control has been developed for the sustainable management of Brazilian peppertree. Numerous phytophagous insects have been tested as potential agents but most exhibited broad host ranges and were rejected. However, a thrips Pseudophilothrips ichini is very specific and damaging to the target weed. Recently, July 2019, a permit was issued by USDA/APHIS and this thrips was released in Florida for biological control of Brazilian peppertree. 

Biological control agents in general may fail to establish in the introduced area or may exert less than satisfactory control of the target weed.  These problems may be mitigated by allocation of resources to produce abundant numbers of agents for release, frequent releases of agent at a range of densities and locations, and avoidance of potential factors that exert biotic resistance. The relationship between the target weed and agent may not be well understood, and releases may occur during a period when its unable to exploit the weed. With this agreement we will conduct research that mitigates these potential obstacles. **Approach:**
                        
                        At least 10,000 agents per year onto Brazilian pepper (BP). Monitoring of the agent establishment and impacts on the plants will be conducted quarterly during the year. Thrips will be released within 3 m of either side of the center of the plot and we will release 1,000 - 4,000 thrips per release point. Pre-release site data will be collected such as sex(es) of the BP comprising the canopy section (if flowers/fruit are present for the determination), soil characteristics (type (calcareous, sandy, organic), shading, duff layer thickness/coverage, presence of understory plants (grasses, vines, forbs), and composition of greater plant canopy (exclusively BP, mixed with other woody perennials, BP overshadowed by taller plants like oak or Melaleuca, etc.). Lastly, we will rank the degree of flushing tips on a 0-10 scale. 
When returning to a release point weeks or months after the first/latest release, we will conduct the thrips survey before supplemental thrips are released. Following the thrips counts, each observer will estimate the flush rank as above as well as rank the damage caused by the thrips to different sections of the canopy. Damage will also be ranked on a 0-10 scale. 

1: Ship biological control insects of Brazilian pepper to cooperator during period of performance of agreement
2: Cooperator will release agents and conduct assessments of impact of weed herbivory


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