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Fungi Associated with and Influence of Moisture on Development of Kernel Mold of Hazelnut
J W Pscheidt1, S Heckert1, M Wiseman1
11 Department of Botany & Plant Pathology, Oregon State University, Corvallis, OR 97331; and.
Abstract:
Kernel mold on hazelnuts is defined by the United States Department of Agriculture, U.S.A., as any visible fungal growth either on the outside or inside of the kernel. Only one yeast and one filamentous fungus have been associated with kernel mold of hazelnut in Oregon. In this report, fungi were isolated from kernels with mold and identified using morphological and molecular characters. Penicillium spp. were isolated most often from kernels with mold, but species of Aspergillus and Cladosporium and Diaporthe rudis were also frequently isolated. Additional fungi from three other genera were also isolated. All of the same fungi were also isolated from symptomless kernels. Eremothecium coryli or Ramularia sp. previously associated with kernel defects in Oregon were not found associated with symptoms of kernel mold. Incidence of mold was the highest when nuts were incubated in moist chambers on wet, nonautoclaved orchard soil and was significantly higher than kernel mold found in nuts incubated on either air-dried soil or wet, autoclaved soil. Preventing hazelnuts from coming in contact with wet soil in the field using elevated wire screens resulted in significantly less mold development in two out of three years evaluated. Nuts on screens had a greater chance to dry out between rainstorms as measured by significantly lower nut moisture levels at harvest.
Insights
Hazelnut kernel mold is caused by various fungi, often found even in symptomless nuts. Preventing soil contact with elevated screens significantly reduces mold incidence by keeping nuts drier.
Area of Science:
- Agricultural Science
- Plant Pathology
- Mycology
Background:
- Kernel mold in hazelnuts is defined by the United States Department of Agriculture as visible fungal growth on or within the kernel.
- Previous associations of specific fungi with hazelnut kernel defects in Oregon were limited.
Purpose of the Study:
- To identify fungi associated with hazelnut kernel mold using morphological and molecular methods.
- To investigate the influence of environmental conditions and field practices on mold incidence.
Main Methods:
- Fungal isolation from moldy and symptomless hazelnut kernels.
- Identification of fungi using morphological and molecular techniques.
- Incubation experiments on different soil types and field trials with elevated screens.
Main Results:
- *Penicillium* spp. were the most frequently isolated fungi, alongside *Aspergillus*, *Cladosporium*, and *Diaporthe rudis*. The same fungi were found in symptomless kernels.
- Mold incidence was highest when nuts were incubated on wet, non-autoclaved soil.
- Elevated wire screens significantly reduced mold development by maintaining lower nut moisture levels.
Conclusions:
- Multiple fungal species, including *Penicillium*, *Aspergillus*, and *Cladosporium*, are associated with hazelnut kernel mold.
- Contact with wet soil is a significant factor in mold development.
- Field practices like using elevated screens can effectively mitigate hazelnut kernel mold by promoting drying.
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