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Marigold - Stem canker (Botrytis cinera)

Stem canker on marigold caused by Botrytis cinera
Stem canker on marigold caused by Botrytis cinera

Botrytis cinera causes leaf spot and blight, stem and crown rot, bulb rot, and flower blight on numerous woody, ornamental, and vegetable species. It is very common in the environment and attacks injured or senescent tissue.

Botrytis species can only be controlled by management of environmental conditions, sound cultural practices, and fungicide applications. Control weeds and remove plant debris. Space plants to allow good air circulation, reduce humidity within the canopy, and minimize leaf wetness duration. Improve horizontal air flow with fans. Reduce humidity by a combination of heating and venting in the evening, particularly when warm days are followed by cool nights Water in the morning if practical. Fungicides appropriate for Botrytis include26 GT, 26/36, Compass, Cleary's 3336, Botran, Decree, Daconil, Dithane,Heritage, Exotherm Termil, Sextant, Protect DF, and Medallion. Check labels for host appropriateness. Resistance to Cleary's 3336, 26 GT, and Sextant has been reported in Botrytis populations. Always alternate fungicide applications between materials with different modes of action to prevent resistance development.