Antifungal Properties of the Insect Alarm Pheromones, Citral, 2-Heptanone, and 4-Methyl-3-Heptanone

Publisher Website
Google Scholar
Abstract
Compounds utilized by insects for chemical communication were variably toxic to fungal species representing the genera Pythium, Rhizoctonia, Diplodia, Fusarium, Penicillium, Gliocladium, Cunninghamella, Paecilomyces, Trichophyton, and Microsporum. The in vitro fungitoxicity of the insect alarm pheromone citral against fungal pathogens of man was comparable to that reported for the antifungal antibiotic Amphotericin B. Citral was less active against the selected fungal pathogens of plants, and fungi isolated from ant larvae, than it was against the dermatophytes. The pheromones, 2-heptanone and 4-methyl-3-heptanone, were less fungitoxic than citral. Significantly, none of the pheromones enhanced fungal growth. Complete inhibition of radial colony growth after five days of incubation occurred with the effective concentration ranges of the various pheromones extending from 20–40 ppm up to 15,000–20,000 ppg. The degrees of inhibition produced by concentrations less than that required for complete inhibition are also described. In addition, the concentration ranges completely inhibiting spore germination of the entomogenous fungi are presented; these ranges extended from 100–200 ppm up to 5,000–10,000 ppm.