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circular pattern of mold on quince Could someone explain why mold on my quinces grows in well separated circles around a center? To make clear, what I mean I post the picture ![enter image description here](

Looks like you may have _Monilinia fructigena_ , brown rot, or at something similar (possibly also called brown rot, but from a different species). This pattern isn't special to quince, but to this fungus.

The formation of these rings is called "zonation", and the concentric rings are from areas of growth that are primarily spore-forming versus not.

Hall (1933) gives an extensive description of the different factors necessary for observing this growth pattern, but ultimately the key factor is _light_. Patterns of light-and-dark conditions while the fungus spreads causes alternating phases of growth, with one phase comprised of more sporulation.

Another source: <

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Byrde, R. J. W., & Willetts, H. J. (2013). The brown rot fungi of fruit: their biology and control. Elsevier.

Hall, M. P. (1933). An analysis of the factors controlling the growth form of certain fungi, with especial reference to Sclerotinia (Monilia) fructigena. Annals of Botany, 47(187), 543-578.

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