Location: Invasive Species and Pollinator Health
Project Number: 2030-22000-033-000-D
Project Type: In-House Appropriated
Start Date: May 13, 2021
End Date: May 12, 2026
1) Discover, identify and prioritize the development of new biological control agents for targeted invasive weed and arthropod pests such as medusahead and bagrada bug. Subobjective 1A: Determine point(s) of origin of ice plant. Subobjective 1B: Discover, identify, and prioritize candidate agents of cheatgrass, medusahead and ice-plant. Subobjective 1C: Discover, identify and prioritize candidate agents of bagrada bug. 2) Evaluate the host range, biology, and potential efficacy of prospective biological control agents for weed and arthropod pests such as French broom and bagrada bug. Subobjective 2A: Deleted. Subobjective 2B: Evaluate host range, biology and potential efficacy of candidate agents on yellow starthistle, Russian thistle, French broom, cheatgrass, medusahead, ice plant, and arundo. Subobjective 2C: Evaluate host range, biology and potential efficacy of candidate biocontrol agents of bagrada bug. 3) Release permitted biological control agents targeting terrestrial weed and arthropod pest targets such as yellow starthistle, Cape-ivy, and spotted wing drosophila, and determine their establishment, dispersal, efficacy, influence on pest populations, benefits for native plant communities or crops, and suitability for integration into integrated weed and arthropod pest management plans. Subobjective 3A: Rear, release and evaluate a new biological control agent of yellow starthistle. Subobjective 3B: Release and evaluate biological control agents on bagrada bug and spotted-wing drosophila. Subobjective 3C: Examine ecological impacts of Cape-ivy biocontrol and implications for integrated management.
Under Objective 1, we will determine the origin of crystalline ice-plant by sampling the invaded range in California and native ranges in South Africa and Mediterranean Europe. Genetic analyses will involve chloroplast and nuclear DNA. We will isolate soil microbes associated with medusahead and cheatgrass and determine best candidates. Surveys will be conducted in California, Nevada and Oregon and will include determination of symptoms and culturing. We will survey crystalline ice plant in South Africa and the Mediterranean and determine best candidate agents on the basis of host specificity and ability to reduce growth and reproduction. We will identify and prioritize candidate agents of bagrada bug that can attack eggs through surveys in South Africa and Kenya. Under Objective 2, we will determine the host specificity and efficacy of one candidate agent each targeting yellow starthistle, Russian thistle and French broom. We hypothesize that these agents will develop and reproduce only on the targeted weed. Biological safety will be examined in no-choice and choice tests. Candidate impact on plant biomass and seed production will be examined in quarantine and in the native range. We will quantify the host range and efficacy of candidate agents of medusahead and cheatgrass. Microbial candidates will be evaluated for inhibition of root development or seed germination. Insects or mites will be evaluated for ability to reduce growth and reproduction. We hypothesize that one host-specific and efficacious agent of crystalline ice plant will be found. We will conduct host range and efficacy tests as for other weeds. We hypothesize that the arundo leafminer can be reared on a California isolate of its fungal associate. We will isolate the leafminer from its native fungal isolate and parasitic nematode. We will assess host specificity of two candidate parasitic wasp species targeting bagrada bug eggs by comparing attack on native plant bugs and the pest, and ability to kill eggs. Under Objective 3, we will increase production of a newly-permitted rosette-feeding weevil for biological control of yellow starthistle. We will develop an artificial diet to facilitate mass-rearing and refine plant-based rearing. We hypothesize that this weevil will establish on and negatively impact yellow starthistle. Releases will be performed in the coastal hills, Central Valley, and Sierra foothills. We will assess field attack rates by resident enemies on bagrada bug eggs by attracting native natural enemies, and cameras and traps will be used to identify species. Searches will also be made for a non-native natural enemy that may already be present. We will release the first permitted biocontrol agent targeting spotted-wing drosophila in the U.S. and will verify establishment and efficacy. If the new enemy fails to establish, we will study native enemies. We hypothesize that the Cape-ivy shoot tip-galling fly will reduce density and flowering of this weed and increase native plant diversity. Biocontrol will be integrated with physical removal. Where the fly fails to establish, we will release a leaf-mining moth.