Epidemiology and Fungicide Sensitivity of Grape Late Season Bunch Rots in the Mid-Atlantic
Epidemiology and Fungicide Sensitivity of Grape Late Season Bunch Rots in the Mid-Atlantic
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Date
2022
Authors
Cosseboom, Scott David
Advisor
Hu, Mengjun
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Abstract
This project aims to improve the management of late season bunch rots of grape (LSBR) whichcan be caused by a wide range of fungal pathogens. LSBR collectively have been an increasing
issue in Mid-Atlantic vineyards, severely affecting grape yield and quality. Despite intensive
fungicide spray programs and cultural practices, severe LSBR epidemics threaten the budding
Mid-Atlantic wine industry. The basic plant pathological variables of host, pathogen, and
environment were investigated to improve knowledge of the diseases involved, and therefore
improve management strategies. The most common causal agents of LSBR in the Mid-Atlantic
were found to be Botrytis cinerea and Colletotrichum spp. and the species identity of less
common fungi was also investigated. The next most prevalent fungi associated with LSBR,
Alternaria alternata, Aspergillus uvarum, and Neopestalotiopsis rosae were evaluated for
pathogenicity in field experiments through the artificial inoculation of grape clusters. Second, the
sensitivity of A. uvarum, B. cinerea, and N. rosae to commonly used chemical classes of
fungicides was tested. Lastly, the optimal infection conditions and timing for Colletotrichum spp.
were evaluated in laboratory, field, and greenhouse experiments, resulting in a quantitative
inoculum tracking technique and a disease prediction model. These experiments were focused on
solving practical and important disease management issues experienced by local grape growers,
while conducting novel research that was applicable to the broader science community. Beyond
the increased knowledge of the etiology and epidemiology of LSBR, the conclusions of this
research could lead to reformed LSBR management strategies with the elimination of
unnecessary and ineffective fungicide applications, increased accuracy and timing of
management efforts, and increased marketable grape yield.