Rhizoctonia Blight
Rhizoctonia solani Kühn
Rhizoctonia zeae Voorhees
Symptoms: Disease can be expressed as seed decay, pre-emergence
and postemergence damping off, stem lesions on seedlings, or stem
canker on more mature plants. Invasion of sheath and blade tissue
can cause a banding pattern. The midrib is usually the last part
of the leaf killed. Mature plants have considerable accumulation
of dead brown leaves around the base. Individual culms may be
killed. The root system is reduced, with extensive killing and
discoloration.
Pathogen and disease characteristics: Rhizoctonia
species often survive in soil as melanized hyphae and sclerotia,
often associated with plant debris. R. solani forms yellow-brown,
matlike stroma and distinct sclerotia in culture. R. zeae
forms a white to pink mycelium and spherical, reddish brown sclerotia
immersed throughout agar medium. Classification of Rhizoctonia
species is currently based on hyphal characteristics and colony
morphology in culture (Sneh et al. 1991).
Host range: Nearly all plants are susceptible to one
or more anastomosis groups of R. solani or binucleate Rhizoctonia
species. Some host specificity exists among the different anastomosis
groups of R. solani. Pathogens of pearl millet have not
been examined for anastomosis compatibility. R. zeae is
primarily a pathogen of many different grasses.
Geographic distribution: On pearl millet: United States,
Tanzania (Mbwaga et al. 1993).
Nomenclature discrepancies: Synonyms: Pellicularia
filamentosa (Pat.) Rogers f. solani (Kühn) Exner.
Alternative names for the disease: Banded sheath, leaf
blight, soil rot.
Seed transmission: Not known to be transmitted by seed.
Konde et al. (1980) has reported isolation
of Rhizoctonia bataticola from seed, but the fungus is
now considered Sclerotium bataticola Taub [teleomorph:
Macrophomina phaseolina (Tassi) G. Goid.] .
Primary citations: Luttrell
1954, Weber 1963.
United States
Department of Agriculture
Agricultural
Research Service
The material on this page is in the public
domain.
Original posting: June 5, 1999.
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