the exception that all fruit was packed within a few hours after wash- 

 ing or inoculating. Also, the severity of the washing treatment was 

 varied to determine its effect on the susceptibility of the fruit to 

 infection. To ascertain the effect of a heavily contaminated wash- 

 ing solution on the development of decay, several rotten apples bear- 

 ing large quantities of blue mold spores were added to the acid tank 

 in one of the treatments and omitted in another; in these treatments 

 the fruit was not subjected to inoculation subsequent to washing. 



The 1941 work was undertaken to determine whether results com- 

 parable with those obtained in the previous three seasons could be 

 obtained with naturally inoculated apples handled under commercial 

 conditions. The Delicious apples used in this experiment were ob- 

 tained from an orchard near Brewster, Wash., the fruit from which 

 had shown serious amounts of lenticel decay over a period of years. 

 The apples were fully mature when harvested and a few showed 

 slight water core. A flood washer containing sodium silicate and 

 hydrochloric acid was employed to clean the fruit. The apples were 

 wrapped with oiled wrappers, packed in standard boxes, and held at 

 31° F. at a relative humidity of 85 to 87 percent. 



The inoculum used in 1938 consisted of blue mold spores washed 

 from the surface of naturally infected apples. During the succeeding 

 2 years a pure culture of Penicillium expansum was employed, the 

 spores being obtained from inoculated fruit or from petri-dish cultures. 



The details of other methods employed in some of the tests are 

 presented in conjunction with the results under the appropriate 

 headings. 



FACTORS RELATED TO BLUE MOLD INFECTION 



Lenticels 



In order to understand better the role of lenticels in blue mold 

 infection, after different treatments in 1939 and 1941 epidermal 

 tissues were stained by immersing the fruit in a solution of methylene 

 blue. Clements (4), 1 whose method was followed in the present 

 study, learned that after the treatment an open lenticel has a distinct 

 halo of dye in the underlying parenchymatous tissue and that a 

 closed lenticel remains uncolored or shows only a surface absorption 

 of the dye. This method was used also by Baker and Heald {2) in 

 studying factors affecting the incidence of lenticel infection by blue 

 mold. 



The details of the 1939 study are given in table 1. In only one 

 lot (Lower N aches) did the number of lenticels on the pale and blush 

 sides of the fruit differ significantly, and in only the Tieton apples 

 were there significantly more open lenticels on one side than on the 

 other. The lots did not differ significantly in the number of open or 

 total lenticels on both sides of the fruit. The lot from Wiley Heights, 

 which had the most lenticel invasions by blue mold, did not have the 

 most open lenticels. (See table 6, p. 15.) Some factor related to the 

 physiological condition of the lenticular tissue probably was re- 

 sponsible for the increased susceptibility of this lot. 



The significantly greater number of open lenticels in the washed 

 lots was correlated well with the higher percentage of lenticel infec- 

 tions found in the washed fruit. (See tables 4 and 5, pp. 9 and 10.) 



1 Italic numbers in parentheses refer to Literature Cited, p. 19. 



