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Determining the effects of inoculum concentration and wounding on the development of fruit rot of winterberry holly

Shan Lin: The Ohio State University

<div>Cut stems of winterberry holly carrying brightly colored berries are traditionally used for holiday decorations. In the past few years, a fruit rot caused by a fungal complex including <em>Alternaria alternata, Diaporthe </em>sp<em>., Colletotrichum fioriniae</em> and <em>Epicoccum</em> <em>nigrum</em>, has been associated with significant yield reduction or complete crop loss. Understanding the role of inoculum concentration and wounding on symptoms development may be useful to identify effective management strategies. To this extent, we point inoculated each of the four pathogens separately at four spore concentrations ranging from 10<sup>3 </sup>to 10<sup>6 </sup>conidia/ml on wounded and unwounded mature winterberry ‘Sparkleberry’ fruit in a detached fruit assay. Six replicates of ten fruit per treatment were arranged in a randomized complete block design and incubated in a moist chamber. Disease development was evaluated for up to six weeks. All pathogens at all concentrations could infect both wounded and unwounded fruit, but disease on wounded fruit developed faster and resulted in higher incidence. Disease severity increased as spore concentration increased. However, <em>E. nigrum</em> inoculum resulted in low disease severity (<11%) at all concentrations. These results indicate that cultural practices that can reduce inoculum concentration in the field and protect fruit from injury may reduce disease severity.</div>