Sustainable Management Strategies for Acarine Pests of Industrial Hemp (Cannabis sativa subsp. sativa L.)

Industrial hemp (Cannabis sativa subsp. sativa L.) is an emerging crop in Florida, generating $445 million in 2024. However, it is highly susceptible to acarine pests, including spider mites (Tetranychidae), broad mites (Tarsonemidae), and russet mites (Eriophyidae). Management options are limited due to a few federally registered products approved by the Florida Department of Agriculture and Consumer Services (FDACS-DPI). Laboratory bioassays were conducted on hemp leaf discs infested with Tetranychus urticae, T. gloveri, Polyphagotarsonemus latus, or Aculops cannabicola, and treated with biorational pesticides (citric acid, rosemary, thyme, sesame, garlic, and mineral oil) at maximum label rates. Citric acid and garlic oil were most efficacious against T. urticae, while garlic and thyme oils were most efficacious against the other species, causing over 80% mortality. Greenhouse trials confirmed the efficacy of citric acid and garlic oil against T. urticae, achieving 60–80% mortality within 24 h. Predatory mites (Amblyseius swirskii, A. andersoni, Neoseiulus californicus, Galendromus occidentalis) were evaluated against A. cannabicola, with A. swirskii showing the highest predation (≈20 adults/24 h) and reproduction. Compatibility tests indicated thyme and garlic oils did not significantly affect A. swirskii survival (>70% alive after 24 h). These findings support integrated pest management strategies for hemp acarine pests.