Practices to Reduce Postharvest 

 Pear Diseases 



Eugene Kupferman 



Washington State University Tree Fruit Research 



& Extension Center, Wenatchee 



Robert Spotts 



Oregon State University Mid-Columbia Agricultural 



Research & Extension Center, Hood River 



David Sugar 



Oregon State University Southern Oregon 



Research & Extension Center, Medford 



The fniit grower plays a critical role in de- 

 termining the quality of finiit delivered to the 

 consumer. This is true even in the area of dis- 

 eases that show up in the packinghouse. Grow- 

 ers must begin control procedures in the orchard 

 for fruit diseases which appear long after har- 

 vest. Preventing wounds, which are the sites 

 for disease infection, is a critical responsibility 

 of the grower. 



Postharvest diseases cost everyone money - 

 - disease reduction in the orchard is less costly 

 than cullage after storage. Cullage means slow 

 movement of fruit in the packinghouse, an ex- 

 pensive job of repacking, or even rejection of lots 

 in the marketplace. We will review preharvest 

 factors affecting postharvest decays of pears and 

 discuss postharvest control within the storage 

 and packinghouse. 



Information About the Diseases 



The major postharvest diseases of pears are 

 caused by fungi. Especially important in the 

 Pacific Northwest are the diseases Gray Mold 

 (Botrytis cinerea), Blue Mold {Penicillium 

 expansum), Coprinus rot (Coprinus spp.), Mucor 

 rot {Mucor piriformis), side rot (Phialophora 

 malorum), and bull's-eye rot {Pezicula 



malicorticis). In most cases orchard sanitation 

 and sprays will significantly reduce the amount 

 of diseased fi:^it in the warehouse. 



Gray Mold (Botrytis cinerea^ 



Botrytis rot is a common decay of Anjou 

 pears. This fungus enters through punctures 

 and wounds. Minimize injury to fruit to reduce 

 the amount of decay from this fungus. How- 

 ever, Botrytis also enters through the stem ends 

 of Anjou pears, since the tissue at the tip of the 

 stem remains alive even after the finiit has been 

 picked. Researchers at the Mid-Columbia Re- 

 search Station hoped that Botrytis infection 

 could be reduced by drying stem tissue. Pears 

 were kept up to two weeks at room tempera- 

 ture or four months in cold storage. Unfortu- 

 nately, the stems did not heal. Stem ends ap- 

 parently remain a site for infection even long 

 into the storage period. Botrytis spores on the 

 stem end can grow down the stem and into the 

 fruit flesh, causing decay and eventually 

 Botrytis nest-rot. 



The source of Botrytis spores is in the or- 

 chard. Fungus grows and sporulates abun- 

 dantly on dead and dying plant material found 

 in orchard cover crops, especially during cool, 



16 



Fruit Notes, Summer, 1995 



