Home • Zoophthora radicans ATCC 208865 v1.0
Zoopthora radicans spores germinating on droplets of water precipitated on the plate lid. Photo by Andrii Gryganskyi.
Zoopthora radicans spores germinating on droplets of water precipitated on the plate lid. Photo by Andrii Gryganskyi.

Zoophthora radicans (Bref.) A. Batko 1964 (syn. Entomophthora sphaerosperma, E. radicans, Erynia radicans) ATCC 208865 (ARSEF 4784) is well known representative of the family Entomophthoraceae (Entomophthorales, Entomophthoromycotina). This ubiquitous insect pathogens was found in various ecosystems and agricultural areas in all continents except Antarctica. The ARSEF-USDA fungal collection (Ithaca, New York, USA) preserves over 500 isolates of this fungus mostly from USA, Brazil, Mexico, Argentina, France, Denmark, former republics of Yugoslavia, Israel, Japan. Zoophthora radicans is a typical generalist pathogen able to infect the arthropods from several unrelated families: Lepidoptera, Diptera, Homoptera and Hymenoptera. Many of its numerous hosts are important pests of agricultural crops: aphids, leafhoppers, planthoppers, Nematocera and cabbage flies, hoverflies, pine sawflies, spruce budworms, rice leafrollers, painted bugs; diamondback, tomato, codling and cabbage moth; cabbage loopers, Lepidoptera larvae and potato/tomato psyllids (1). As many other Entomophthorales this fungus mostly infects adult arthropods but also insects’ larvae and nymphaea. Many of its hosts are important pests or diseases vectors for various agricultural crops: spring wheat, rice and other cereals; beans, soybeans, cowpeas, alfalfa, lupin, sunflowers, sugar beets, cabbage, broccoli, peanuts, potatoes, tomatoes, lettuce, artichoke, fruit trees, pines, woody ornamentals. Despite the considerable potential of the fungus as efficient biocontrol agent, there is only one successful record of its use against invasive aphids recently introduced to Australian entomofauna (2).

After penetrating the host’s cuticle with germination hyphae Zoophthora radicans develops inside infected insects hyphal bodies and protoplasts of various length and shape. The dead insects are attached to the substrate by thin threadlike unbranched rhizoids, often aggregated into the pseudorhizomorphs. After utilizing all available nutrition from insect body the fungus develops branched conidiophores, which penetrate the cuticle and forcibly discharge elongated, bitunicate, uninucleate, bullet-shaped primary conidia 19-25×5-6μm. They germinate with mycelium or produce secondary conidia of the same shape and usually of smaller size. Another type of secondary conidia is passively discharged dry lemon-shaped capilliconidia, produced on long thin conidiophores growing from the primary conidia. Resting spores are rare, round, 20-30μm in size, with thick smooth episporium, yellowish colored, with oil droplet inside (3). Zoophthora radicans grows well on the number of nutritive media in the laboratory conditions, producing many of these vegetative and propagative structures including hyphae, conidiophores, primary and secondary conidia of both types.

References:

1. U.S. Department of Agriculture, Agricultural Research Service, Biological Integrated Pest Management Research Unit (2016). ARS Collection of Entomopathogenic Fungal Cultures (ARSEF). U.S. Department of Agriculture, Agricultural Research Service. DOI: 10.15482/USDA.ADC/1326695
2. Nielsen C, Wraight SP. Exotic aphid control with pathogens. In: Hajek AE, Glare TR, O'Callaghan M, editors. Use of microbes for control and eradication of invasive arthropods: Springer (2009): 90–113.
3. Batko A. On the subgenera of the fungus genus Zoophthora Batko 1964 (Entomophthoraceae). Acta Mycologica (1966) 2: 15-21.