Disease Note

First Report of Botrytis cinerea on Kenaf in Spain. A. De Cal, Departamento Protección Vegetal, CIT-INIA, Madrid, Spain. P. Melgarejo, Departamento Protección Vegetal, CIT-INIA, Madrid, Spain. Plant Dis. 76:539. Accepted for publication 4 December 1991. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-0539E.

Kenaf (Hibiscus cannabinus L.) is intended to be introduced in Spain as an alternative to crops with surplus production. During September-October of 1990 and 1991, several experimental fields of kenaf in northern Spain and in the Canary Islands were affected by gray mold caused by Botrytis cinerea Pers.:Fr. Shoots of infected plants showed necrotic areas, and some lesions completely encircled the stem; parts above this area died, and lodging occurred. The mycelia and gray conidia of the fungus were apparent on lesions. Hyaline, one-celled conidia and conidiophores conformed to those described as B. cinerea. The fungus was isolated consistently from diseased tissues onto potato-dextrose agar (PDA). Pathogenicity was proved by application of B. cinerea as 7-day-old mycelial plugs with or without PDA directly to the shoot and by application of a piece of PDA culture of the fungus to a small incision made in the shoot. Five lI6-day-old greenhouse-grown plants were tested three times by each inoculation method. Symptoms obtained with all inoculations developed after 5 days and were identical to those observed in natural field infections. The fungus was readily reisoiated on PDA from artificially inoculated kenaf. This is the first report of B. cinerea on kenaf in Spain and in Europe. Infected kenaf had to be harvested I mo before the optimal date, with consequent losses in yield and quality of the fiber. Gray mold may potentially affect kenaf seed production in the Canary Islands.