Type: report

Article abstract: In 2016, the North Coast Cactus Nursery (Nursery), located in Escondido, California, was established to provide native plant materials to support restoration projects of coastal cactus wren (Campylorhynchus brunneicapillus) habitat in San Diego County (County). Establishment of the Nursery was led by the San Diego Association of Governments (SANDAG), San Diego Management and Monitoring Program (SDMMP), and the City of San Diego, with the focus of providing a source population for propagation of Opuntia littoralis. Since the establishment of the Nursery through 2018, over 8,000 O. littoralis were supplied to out-planting sites in the County (SD Zoo 2018). In 2021, AECOM was tasked with implementing renovations for the Nursery (e.g., replacement of existing weed barrier, repair and expansion of the irrigation system, and replacement of shade structure on site). During the onsite kick-off meeting in April 2021, AECOM ecologists observed O. littoralis expressing signs of stress and speculated that these were due to a disease uncommon to the species. Initial observation photographs and samples were collected and sent to the University of California Davis’s (U.C. Davis) Fruit and Vegetable Plant Pathology Lab (U.C. Davis Lab), where Fusarium brachygibbosum, a fungal pathogen, was recovered. This was the first time this specific pathogen-host relationship had been documented, which raised concerns by County land managers that observed similar symptoms in cacti populations on their lands. These findings led to the development of the pathogen pilot study (study) discussed in this report. Because of the important ecological role that southern California cacti populations play in coastal cactus wren habitat, and concern of potential fungal pathogen spread, the study was developed to investigate the distribution of affected cacti. The goal of the study is to support a large-scale observation and testing effort for cacti populations that are either out-plantings sourced from the Nursery, original collection points for the establishment of the Nursery, or native populations unassociated with the Nursery that are speculated to have similar symptoms. In spring and summer 2022, AECOM identified survey areas and conducted surveys throughout the County to document O. littoralis population health and collect samples of potentially affected plants. This report documents the methodology and results of the surveys conducted by AECOM