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Some investigations of cause and control of winter pear storage rots in the Rogue River Valley, Oregon MacSwan, Iain Christie


A survey of inspection records of Anjou and Bosc pears shipped to market between November 1, 1956 and March 30, 1957 show storage rots to be an important problem of the Rogue River valley pear industry. Considerably more rot occurred in the Bosc than in the Anjou pears. Tissue isolations from the common blue mold and gray mold rots consistently yielded Penicillium sp. and Botrytis sp. respectively. Isolations showed Cladosporium sp. to be almost always associated with a brown, superficial rot of Anjou and with a brown-black rot of Bosc pears. Packing-house tests of three concentrations of Stop-Mold B showed it to be an effective rot-preventative. An apparent improvement in the control of rots with increased concentration of Stop-Mold B solution occurred in one lot of pears. Another lot showed an apparent decrease in control of rots with increased concentration of this fungicide. Packing-house tests of fungicides for prevention of rots were conducted in 1958 and 1959. Of the nine fungicides tested, Busan 50 was the most effective for rot control but resulted in a severe, brown skin discoloration. The commonly used post-harvest-dip chemical, Stop-Mold B, ranked high in all of the tests and is considered to be the best of the fungicides tested. The high percentage of storage rot spots with a broken surface indicates the importance of handling fruit carefully to avoid injury. Penicillium was the most prevalent rot of the pears examined during these investigations. Next was Cladosporium rot, then Botrytis rot. Cladosporium rot is shown to be a major storage rot of winter pears in the Medford area and is not necessarily associated with skin breaks.

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