Fungus Isaria fumosorosea General Information

Isaria fumosorosea, was first described as Paecilomyces fumosoroseus by M. Wize in 1904. It is now considered a very effective fungal entomopathogen. It was discovered by M. Wize in a suffering sugar beet weevil in the Ukraine but has a huge distribution range. Isaria fumosorosea is a species complex rather than a single species. This means there are wide variations. Undoubtedly there will be taxonomic revisions of this group in the future (Zimmermann, 2008). Isaria fumosorosea is found in the soil, on plants, in the air, on every continent in the world except Antartica (Cantone and Vandenberg, 1998), (Zimmerman, 2008)  It has been found to effect over forty species of arthropods. Susceptible organisms include some of the more problematical horticultural pests. A few mentionables being, whiteflies, thrips, aphids and termites. (Smith, 1993; Dunlop et al. 2007; Hoy et al. 2010) Because of its wide range of arthropodial host, it has received significant attention in research as a biological control agent. Much of the research has been focused on controlling the whitefly, Bemisia tabaci. We have an interesting post describing the use of Isaria in combination with  Lecanicillium and Paecilomyces lilacinus. We have found it quite effective. It is a product that will convince the traditional horticulturalist to think “microbe”.

 Fungus Isaria fumosorosea Mode of Action

Like most entomopathogenic fungi, Isaria fumosorosea, infects its host by dissolving the insects cuticle (Hajek and Leger, 1994). Various metabolites allow the Isaria fumosorosea to penetrate the host insect and inhibit its regulatory system. The active enzymes exuded by Isaria fumosorosea include proteases, chitinases, chitosanase, and lipase (Ali et al. 2010). These allow it to breach the arthopods cuticle and disperse through the hemocoel.  Isaria fumosorosea also produces beavericin (Luangsa-ard et al. 2009). Beavericin paralyzes the host cells (Hajek and Leger, 1994). Affectable arthropods exposed to blastospores and conidia show slowed growth and high counts of mortality (Dunlap et al. 2007).

 Fungus Isaria fumosorosea Mode of Application

Worldwide, it is currently used in 8 different mycoacaricides and mycoinsecticides (Faria and Wraight, 2007). All are considered safe and non-toxic to humans (Dalleau-Clouet et al. 2005)  Perhaps the most interesting aspect of its use is that it has little effect on most off target beneficial insects when used correctly (Zimmerman, 2008). Tests show that the fungus is not toxic to mammals nor birds as well as humans.

Isaria fumosorosea can and should be applied in combination with other entomopathogenic fungus such as Lecanicillium and Beauvaeria. The diluted mix is sprayed not only on the upper and lower leaves, but over the entire phylosphere of the plant in the soft morning or evening light. Keep in mind there are several factors which influence the growth and stability of Isaria fumosorosea. These include temperature, relative humidity, radiation, and the host plant of the target insect (Zimmerman 2008). It works best at temperatures between 22⁰C and 30⁰C (72⁰F-86⁰F), and requires high humidity. Exposure to sunlight can have serious negative effects on survival of I. fumosorosea (Zimmerman 2008). Studies demonstrate that UV radiation, particularly wavelengths in the UV-A and UV-B(400 to 280 nm) region are the most problematical.

Isaria fumosorosea was registered as an active ingredient in a Manufacturing Use Product and in one End-use Product for non-food use in greenhouses in October 1998 in the USA. These products are now labeled for non-food and for agricultural food uses. An exemption from tolerance was established in 40 CFR 180.1306 in September 2011.


  • Ali, S., Huang, Z., and Ren, S. 2010. Production of cuticle degrading enzymes by Isaria fumosorosea and their evaluation as a biocontrol agent against diamondback moth. Journal of Pest Sci 83: 361-370.
  • Cantone, F. and Vandenberg, J. 1998. Intraspecific diversity in Paecilomyces fumosoroseus. Mycol. Research 102 (2) 209-215
  • Dalleau-Clouet, C., Gauthier, N., Risterucci, M., Bons, C., and Fargues, J. 2005. Isolation and characterization of microsatellite loci from the entomopathogenic hyphomycete, Paecilomyces fumosoroseus. Molecular Ecology Notes 5: 496-498
  • De Faria, M., and Wraight, S. 2007. Mycoinsecticides and Mycoacaricides: A comprensive list with worldwide coverage and international classification of formulation types. Biological Control 43: 237-256
  • Dunlap, C., Jackson, M., and Wright, M. 2007. A foam formulation of Paecilomyces fumosoroseus, an enotmopathogenic biocontrol agent. Biocontrol Science and Technology 17 (5/6): 513:523
  • Hajek, A., and Leger, R. 1994. Interactions between fungal pathogens and insect hosts. Annual Review of Entomology 39:293-322
  • Luangsa-ARD, J., Berkaew, P., Ridkaew, R., Hywell-Jones, N., and Isaka, M. 2009. A beauvericin hot spot in the genus Isaria. Mycological Research 113: 1389-1395.
  • Smith, P. 1993. Control of Bemisia tabaci and the potential of Paecilomyces fumosoroseus as a biopesticide. Biocontrol News and Information, 14, 71-78N
  • Zimmerman, G. 2008. The entomopathogenic fungi Isaria farinosa (formerly Paecilomyces farinosa) and the Isaria fumosorosea species complex (formerly Paecilomyces fumosoroseus): biology, ecology, and use in biological control. Biocontrol Science and Technology 18 (9) 865-901.