Location: Invasive Plant Research Laboratory
Project Number: 6032-22000-013-123-I
Project Type: Interagency Reimbursable Agreement
Start Date: Nov 20, 2023
End Date: Apr 30, 2025
Objective:
The primary purpose of this project is to reduce populations of the aggressive invasive weed, Brazilian peppertree, by the strategic deployment of a newly approved biological control agent. This environmentally safe, cost-effective, and sustainable means of weed control will be accomplished with the 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 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 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. 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) Increase production of laboratory colonies of the thrips biological control agent for field release.
2) Continue field releases on stakeholder lands and evaluate agent impact and persistence.
3) Determine how plant genetic variations impact plant vigor and susceptibility to agents across a latitudinal gradient.
Approach:
After 4 years the thrips appears to be persisting in numerous release sites and research suggests these goals and objectives described herein can be achieved. Preliminary results suggest, but further study needs to confirm, that release strategies with large numbers of individuals (over 1000 individuals) and frequent releases in diverse habitats will assist in agent establishment.
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.
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 releases will be conducted as needed to maximize the chances of establishment and impact. Sub-objective 3 will shed light on how plant genotypes interact with the environment to impact plant vigor and susceptibility to agent feeding damage. This will be accomplished with a replicated field experiment at 5 different sites along a latitudinal gradient spanning several climate zones in the invaded range. Plant demographic data will be collected as well as thrips performance data. This will be of value to our stakeholder as it will increase understanding of how the agent may perform at air bases across the state.
