Optimization of host-parasite population ratio of Floracarus perrepae for release against the invasive fern Lygodium microphyllum

The United States Department of Agriculture – Invasive Plant Research Laboratory started limited production of a biological control mite, <em>Floracarus perrepae</em>, in 2008 for release against the invasive fern <em>Lygodium microphyllum</em>. Mass rearing of the biological control agent was initiated in 2014 as part of a mass rearing and broader release effort associated with the Comprehensive Everglades Restoration Plan. In late 2021, relatively simple adjustments made to plant and agent mass rearing protocols produced exponential increases in <em>F. perrepae</em> colony productivity. This increase is attributed to several key changes in colony maintenance that optimized the host-parasite population ratio. We developed a systematic method involving a weekly plant readiness criterion and a predefined sequence of stages to select plants for release, which ensures galls are correctly aged to maximize mite numbers.
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This project was partially funded by the USDA, through the Comprehensive Everglades Restoration Plan (CERP) (USDA agreement 58-6032-1-001) co-directed by the South Florida Water Management District and U.S. Army Corps of Engineers, and through Southwest Florida Water Management District (USDA agreement 58-6032-3-003).