jaii.21, i9i8 Irrigation Experiments on Apple-Spot Diseases 135 



but the affected tissue is firmer than in the case of bitter-pit and there 

 is no association with the vascular bundles. The early stages of Jona- 

 than-spot are confined to the color-bearing cells of the skin of the apple. 

 Drouthspot is characterized by the checking of the growth at certain 

 points on the apple without the production of any large quantity of corky 

 tissue. Cork differs from the drouthspot in the presence of compara- 

 tively large spots of brown corky tissue and in the fact that these are 

 usually rather deeply seated in the flesh of the apple. Blister is a super- 

 ficial lesion associated with cork and characterized by its blister-like 

 appearance. 



(2) Drouthspot has been produced by sudden and extreme drouth. 

 It has occurred on trees that were favorably located as well as on those 

 that were growing under rather unfavorable soil conditions. Cork is 

 apparently also a drouth effect, but it differs from drouthspot in the 

 fact that its occurrence is usually associated with certain peculiar soil 

 types. 



(3) Experiments have shown that there is a close relationship between 

 the soil-water supply of the orchard and the development of bitter-pit 

 in storage. Heavy irrigation has greatly increased the disease, but not 

 so much as medium irrigation followed by heavy irrigation. Light irri- 

 gation has greatly reduced it, but heavy irrigation followed by light has 

 resulted in the lowest percentage of the disease. Sudden changes in the 

 amount of soil water have apparently not increased the disease. 



(4) Heavy irrigation may have been slightly favorable to the develop- 

 ment of Jonathan-spot, but the contrasts have been too slight to justify 

 definite conclusions. 



(5) Large apples have shown greater susceptibility to bitter-pit than 

 small ones, but with Jonathan apples heavy irrigation increased the 

 disease on the medium-sized fruit as well as on the large, and with 

 Grimes the percentage of increase from heavy irrigation has been even 

 greater on small apples than on large ones. Apparently, large apples 

 are not susceptible to bitter-pit merely because they are large, but 

 rather because of certain conditions under which they become large. 



(6) In 1 91 5 there was more Jonathan-spot on the large apples than on 

 the small ones, but in 191 6 there seemed to be no correlation between 

 size of fruit and severity of disease. 



(7) During the first weeks of cellar storage there was always more 

 Jonathan-spot developed on apples that were picked early than on apples 

 that were picked late, but with longer periods of storage these contrasts 

 seemed to largely disappear. The results indicate, however, a greater 

 susceptibility in the early-picked fruit. 



(8) Bitter-pit was worse on the Jonathan apples that were picked early 

 than on those that were picked late. 



