Some orchards have high levels of Mucor which 

 is related to high soil moisture and an abun- 

 dance of fruit on the ground. When the bot- 

 toms of bins are in contact with contaminated 

 soil, a large number of Mucor spores can be 

 brought into the packinghouse in and on the 

 bins. 



Pears which had fallen on the ground were 

 examined for evidence of fungal spores. Dur- 

 ing harvest most of the fruit on the ground had 

 begun to rot with Gray Mold. One month after 

 harvest most of the fruit was being decayed by 

 Mucor. One method of reducing the number of 

 spores on the orchard floor would be to pick up 

 any of the early maturing fruits (e.g., Bartletts) 

 Ijdng on the ground. These fruits provide nu- 

 trients for the buildup of high levels of fungal 

 spores, which may contaminate and infect later 

 harvested Anjou or Bosc pears. Rodents such 

 as mice and squirrels, as well as insects and 

 rain, are factors in spreading decay organisms 

 throughout the orchard. 



Mucor spores are not easily airborne. This 

 is in direct contrast to Botrytis and Fenicillium 

 spores. To reduce the amount of spores going 

 into the packinghouse, growers can put a layer 

 of gravel or 

 wood chips on 

 the soil surface 

 to insulate the 

 bottom of the 

 bins in the 

 loading area. 

 Thoroughly 

 rinsing the 

 bottom of the 

 bins with wa- 

 ter to remove 

 contaminated 

 soil before the 

 bins go to the 

 packinghouse 

 also would re- 

 duce the num- 

 ber of spores. 



problem in the Medford, Oregon pear-growing 

 district for the past several years. Though the 

 primary causal fungus, Phialophora, has been 

 found on decaying pears in Washington, it is 

 not currently an economic problem there or in 

 the Hood River district. Side rot has been found 

 on Anjou and Comice pears, but the most seri- 

 ous losses have occurred on Bosc. It is a prob- 

 lem of long-term storage; infections become vis- 

 ible in late Dec. or Jan., and incidence of decay 

 increases as the storage season continues. 



Research at the Southern Oregon Experi- 

 ment Station has shown that side rot lesions 

 can be caused by two fungi, Phialophora 

 malorum and Cladosporium herbarum. Typi- 

 cally dark brown, dime-size decay lesions sepa- 

 rate cleanly from adjacent healthy flesh. The 

 color and texture of the decayed tissue vary with 

 the amount of drying due to skin breakage. 

 Both of these fungi are relatively slow-growing, 

 weak pathogens which apparently must wait 

 for fruit to weaken through age before infect- 

 ing. Cladosporium. is sensitive to thiabenda- 

 zole (TBZ), vfhile Phialophora is not. Most side 

 rot in fruit treated postharvest with thiabenda- 

 zole is caused by Phialophora. 



Side Rot 



Side rot 

 has been a 



Table 1 . Decay in attached Anjou pear fhiits inoculated monthly during the 

 growing season in 1980 and 1981. 



Percent decay* caused by 



Week of inoculation 

 before harvest 



Botrytis 

 cinerea 



Mucor 

 piriformis 



Penicillium 

 expansum 



Pezicula 

 malicorticis 



0" 

 6 

 9 



15 



19 



82 

 14 



18 



69 

 















100 



99 



100 



74 



69 



'Decay is the total from evaluations conducted monthly during the growing 

 season, during storage, and after a one-week ripening period. Each value 

 represents the mean of 50 fruits. Researchers made two needle punctures per 

 fruit through drops of inoculum. 



'Fruit were inoculated two days before harvest. 



Fruit Notes, Summer, 1995 



