Location: Invasive Plant Research Laboratory
Project Number: 6032-22000-013-149-I
Project Type: Interagency Reimbursable Agreement
Start Date: Dec 22, 2024
End Date: Dec 21, 2025
Objective:
The primary purpose of this project is to reduce populations of the aggressive invasive weed, Brazilian peppertree, by the strategic deployment of an approved classical biological control agent. This environmentally safe, cost-effective, and sustainable means of weed control will be accomplished with the continued mass production, distribution, and evaluation of the approved thrips, Pseudophilothrips ichini. In addition to saturating stakeholder lands with the insect, methods will be developed to improve the establishment success and spread of the insect.
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 inoculative or inundative releases, 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 or constant across the landscape. This proposal seeks support to conduct research that contributes to maximizing the impact the agents we produce will have on the target weed. The sub objectives are as follows:
1) Maintain production of laboratory colonies of the thrips biological control agent for field release
2) Continue new field releases on stakeholder lands, supplement older releases where appropriate, and evaluate agent impact and persistence for older releases
3) Determine how far thrips have spread from release sites established in prior years and from new release sites initiated this performance period.
Approach:
After 5 years the thrips are persisting at numerous release sites and research suggests these goals and objectives described herein can be achieved. Data suggest that release strategies with large numbers of individuals (over 1,000 individuals) and frequent releases in diverse habitats will assist in agent establishment. Some sites may require a more inundative approach to achieve the levels of control desired.
After completing quarantine host range tests that confirmed the environmental safety of the agent, the continued success of a classical biological control program depends on the mass production, redistribution, and examination of the potential of the approved agent and their limitations to develop outbreak populations. The potential for control of the target weed by small populations of thrips was demonstrated pre-release in quarantine cages where one generation of adult thrips reduced sapling tip number and plant growth by 80%. These results were confirmed under field conditions at sites with optimal thrips performance.
The proposed research described here builds upon work achieved in the previous year of funding through this agreement. Sub-objective 1 will employ the refined mass rearing techniques developed earlier to expand thrips production. Sub-objective 2 will continue the release of the Brazilian pepper thrips on stakeholder lands, with efforts to find new release sites and to monitor existing sites for agent efficacy. Supplemental/inundative releases will be conducted as needed to maximize the chances of establishment and sustained impact. Sub-objective 3 will add a new dimension to agent impact by documenting their dispersal abilities from older release sites and will allow is adjust release site spacing and timing to maximize geographic coverage.
