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Research Project: Discovery and Development of Biological Control Agents for Weeds that are Invasive in the U.S. and Native to Australia and Asia

Location: Office of International Research Engagement and Cooperation

Project Number: 0210-22310-010-00-D
Project Type: In-House Appropriated

Start Date: Oct 14, 2020
End Date: Oct 13, 2025

Objective:
Objective 1: Discover, identify and initiate the development of new biological control agents for invasive weeds that are native to Australia and/or Asia such as Melaleuca, Lygodium, Acacia, Hydrilla, Nymphoides, Azolla and Rotala. Establish high-priority agents by collecting, rearing, and shipping to U.S. collaborators. (non-hypothesis driven) [NP304, C2, PS 2A 2B] Sub Objective 1.1. Discovery and identification of new biological control agents for invasive weeds and developing understanding of basic life history of natural enemies to design rearing methods and host range tests. Ship to U.S. collaborators. Sub Objective 1.2. Development of new biological control agents for invasive weeds. Conduct host specificity tests and assess impact of potential biological control agents. Objective 2: Develop an iterative approach in exploration for biological control agents using a decision process based on Next Generation Sequencing of weed targets in their native and introduced ranges and their natural enemies. (potentially hypothesis driven) [NP304, C2, PS 2B] Objective 3: Selection of biological control agents compatible with chemical and mechanical control or for areas where alternative controls of weed invasions are not feasible. (non-hypothesis driven) [NP304, C2, PS 2C]

Approach:
Objective 1: Develop understanding of basic life history of natural enemies to design rearing methods and host range tests. Conduct host specificity tests and assess impact of potential biological control agents. Foreign exploration will be guided by the center of origin of the weed species (classical and molecular diagnostics), habitat diversity, climate matching, specific phenology and ecology of the targets. Sites for exploration will be identified through the use of herbarium records, local knowledge, and maps of ecological areas. Exploration will be conducted in a systematic manner visiting unique ecological areas in the distribution of targets. Sites will be surveyed at different times of the year, i.e. wet and dry seasons. Agents will be sought which supplement the modes of attack of agents already established in the U.S. Initial molecular screening with mitochondrial markers will be conducted on representative herbivore species collected and the weed target species to provide an indication of genetic diversity and structuring. For selected arthropods the number of life stages, feeding behavior, developmental time of immatures, sex ratio, oviposition behavior of adults, fecundity and adult longevity will be determined in the laboratory and supplemented with field observations. Preliminary host range tests will be designed to predict the field host range of a candidate biological control agents. Studies will also be undertaken to quantify the impact of promising agents for select target species. Objective 2: The prospective and iterative approach tests if provenance determination of the target weed can ensure there is no mismatch between areas of the native range surveyed for herbivores and the introduced ranges in terms of the target host plant. Provenance of the agent (controlling for cryptic species) is an important predictor of efficacy and host specificity of an agent. Objective 3: Investigation of existing data on the biology/host specificity/impact of natural enemies in large data sets will lead to the identification of specific traits that influence the compatibility of agents to produce increased efficiency where alternate or existing controls for target weeds are ineffective. Large data sets on the biology, impact and host specificity of insect herbivores as well as the phenology/demography have been accumulated for weed targets over past decades by our laboratory. Contrasting this information with the weed target’s preferred habitat/s in the invasive range, current success and application of alternative forms of control (chemical/mechanical) and areas where existing released biological control agents have been ineffective, will be used to guide prioritisation of the selection of new biological control agents to be evaluated in Australia or introduced into U.S. quarantine.