Hirsutella thompsonii

Hirsutella thompsonii exemplifies targeted biocontrol: a fungal pathogen specific to eriophyid mites that damage citrus crops. Unlike broad-spectrum entomopathogens, Hirsutella's narrow host range means it attacks pest mites without affecting beneficial insects, predatory mites, or other non-targets. This specificity enables integration with other biological control agents in comprehensive pest management systems.

The fungus produces needle-like spores (conidia) on infected mites, giving dead mites a fuzzy appearance. These spores efficiently transmit between mites in citrus canopies. During humid conditions, Hirsutella can spread rapidly through mite populations, causing epizootics that crash pest densities. The pathogen's dependence on humidity means it works best in tropical and subtropical citrus production; drier conditions limit transmission.

H. thompsonii represents the specialized end of the entomopathogen spectrum. Where Beauveria and Metarhizium succeed through broad host ranges, Hirsutella succeeds through precision. The narrow focus enables ecological integration—because Hirsutella doesn't harm beneficial organisms, it can operate alongside them in complex agricultural ecosystems. Different biocontrol strategies suit different contexts: generalists for broad pest suppression, specialists for precision targeting within integrated systems.