Lecanicillium aranearum

Lecanicillium aranearum is an entomopathogenic fungus that primarily affects arachnids. In modern agronomy, particularly within greenhouse settings, this pathogen is significant not as a primary plant disease, but as a parasite that targets the beneficial predatory mites used for biological pest control.

The causative agent is the fungus Lecanicillium aranearum, which belongs to the group of hyphomycetes. This organism is highly specialized, and its primary hosts are spider mites and their natural predators, such as phytoseiid mites. Its presence can significantly undermine the efficacy of Integrated Pest Management (IPM) programs.

This pathogen impacts a wide range of horticultural crops grown in greenhouses, including tomatoes, cucumbers, and ornamental flowers. The primary danger of this fungus is the depletion of the population of beneficial predatory mites, which are released to manage spider mite outbreaks, ultimately leading to crop damage by the original pests.

Symptoms of the infection involve the death of predatory mites. Upon examination under magnification, one can observe white or yellowish mycelial growth covering the deceased mites. The infected individuals cease their predatory activity, and the colony rapidly declines, leading to a loss of biological pressure against agricultural pests.

Development and spread of the fungus are favored by high humidity (often above 80%) and moderate temperatures ranging from 18°C to 25°C. To prevent and manage this disease, growers should strictly monitor the humidity levels in the greenhouse, ensure proper air circulation to avoid moisture accumulation, and perform regular health checks on introduced biological agents to detect early signs of fungal infection.