Black Root Rot (Thielaviopsis)
Gary W. Moorman, Professor of Plant Pathology
The fungus Thielaviopsis basicola (Berk. & Br.) Ferraris is a soil inhabiting fungus that can cause root rot and branch dieback on a number of woody and herbaceous plants including holly, begonia, geranium, poinsettia, cyclamen, gerbera, and pansy. Soil temperatures between 55 and 65°F generally favor this fungus, particularly if the soil is wet. The fungus can be found in field soil but has also been found associated with commercial peat moss.
- stunting of foliage and root systems
- blackened areas on roots
- yellowing of leaves between the veins or along the margins
- branch dieback
- dark brown, multicelled spores form in the infected roots. The indivudual cells appear to snap apart.
- Light colored spores are formed in a long tapering cell and extruded in chains
- Steam field soil and peat moss. Heat it to 180°F and hold it at that temperature for 30 minutes.
- Apply thiophanate methyl, thiophanate methyl + etridiazole, fludioxonil, or triflumizole as a soil drench. When using thiophanate methyl, it is best to have the pH between 6 and 8 in the drenching liquid.
Holly: Ilex crenata, Helleri, Hoogendorn, Nigra, Green Cushion, Mobjack Supreme and Hetzzi are very susceptible. Ilex vomitoria and Ilex opaca are moderately resistant. English holly (Ilex aquifolium) and Chinese holly (Ilex cornuta) are highly resistant.
Daughtrey, M. L., Wick, R. L., and Peterson, J. L. 1995. Compendium of Flowering Potted Plants. APS Press. St. Paul, MN. 90 pp.
Lambe, R. C. And McRitchie, J. J. 1986. Holly diseases. In, Diseases of Woody Ornamental Plants and Their Control in Nurseries. North Carolina Agricultural Extension Service, Raleigh, NC. 130 pp.
Active Ingredients and Trade Names of the Chemicals
|FRAC Group No.||Risk Level||Class||Active ingredient||REI Restricted Entry Interval||Trade names (EPA Reg. no.)|
|1||3||Benzimidazole||thiophanate methyl||12||3336 (1001-69), OHP 6672 (51036-329-59807)|
|Fungo Flo (51036-329-59807)|
|Systec 1998 (48234-12)|
|Combined 1 products|
|1 + M||thiophanate methyl + etridiazole||Banrot (58185-10)|
Thielaviopsis spores in culture
In a root cell
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Warning! Pesticides are poisonous. Read and follow all directions and safety precautions on labels. Handle carefully and store in original labeled containers out of the reach of children, pets, and livestock. Dispose of empty containers right away, in a safe manner and place. Do not contaminate forage, streams or ponds.
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