Patterns of release of the secondary conidia of Claviceps africana, the sorghum ergot pathogen in Australia

Trials were conducted in southern Queensland, Australia between March and May 2003, 2004 and 2005 to study patterns of hourly and daily release of the secondary conidia of Claviceps africana and their relationships with weather parameters. Conidia were trapped for at least one hour on most (> 90%) days in 2003 and 2004, but only on 55% of days in 2005. Both the highest daily concentration of conidia, and the highest number of hours per day when conidia were trapped, were recorded 1-3 days after rainfall events. Although the pattern of conidial release was different every day, the highest hourly conidial concentrations occurred between 10.00 hours and 17.00 hours on 73% of all days in the three trials. Hours when conidia were trapped were characterized by higher median values of temperature, windspeed and vapour pressure deficit, lower relative humidity, and leaf wetness values of 0%, than hours when no conidia were recorded. The results indicate that fungicides need to be applied to the highly ergot-susceptible male sterile (A-) lines of sorghum in hybrid seed production blocks and breeders' nurseries as soon as possible after rainfall events to minimize ergot severity

Botrytis species on bulb crops

Abstract. 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 rotare two of the most important fungal diseases of onion. The taxonomics of several of the neck rotpathogens 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 leafblight 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 inproduction fields. In both the onion and flower bulb production systems chemicals are still heavily reliedupon to control the major diseases, however, alternative disease management systems also are used andundoubtedly will become increasingly important in controlling the diseases. Infected plants and colonizedplant 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 asapothecia producing ascospores, in onion production areas in New York. The primary inoculum sourcesof B. allii and B. gladiolorum are believed to be infested seed and infected corms, respectively