Botrytis Species on Bulb Crops

A number of Botrytis species are pathogens of bulb crops. Botrytis squamosa (teleomorph= Botrytotinia squamosa) causal agent of botrytis leaf blight and B. allii the causal agent of botrytis neck rot are two of the most important fungal diseases of onion. The taxonomics of several of the neck rot pathogens of onion have been revised on the basis of recent molecular sequence analysis studies. B. allii, B. aclada, and B. byssoidea are now recognized as distinct species causing neck rot diseases of onion. B. cinerea is also pathogenic on onion, primarily causing botrytis brown stain on onion bulbs. B. tulipae, B. elliptica, and B. gladiolorum are important pathogens of flower bulbs and are the causal agents of leaf blight in tulip, lily, and gladiolus, respectively. Leaf blight in the major flower bulb crops is called ‘fire’ referring to the fire-like symptoms occurring on the leaves of flower bulb plants when epidemics occur in production fields. In both the onion and flower bulb production systems chemicals are still heavily relied upon to control the major diseases, however, alternative disease management systems also are used and undoubtedly will become increasingly important in controlling the diseases. Infected plants and colonized plant debris are considered important sources of inoculum for B. squamosa, B. tulipae, and B. elliptica, particularly when sclerotia are formed. Sclerotia of B. squamosa serve as the source of conidia, as well as apothecia producing ascospores, in onion production areas in New York. The primary inoculum sources of B. allii and B. gladiolorum are believed to be infested seed and infected corms, respectively.