94 FUNDAMENTALS OF FRUIT PRODUCTION 



some other rather obscure disorder, so some of the serious troubles of these 

 other fruits may prove eventually to be due directly or indirectly to 

 drought. Rosette and little-leaf are certainly not unknown in the cherry, 

 apricot, plum and pear though little attention has been devoted to them. 



Barss'" records "cork" as of frequent occurrence in pears in Oregon and a 

 "drought spot "or "gum-spot "as not uncommon in prunes. Both are attributed 

 to disturbed water relations. In speaking of the gum-spot of prunes he says: 

 "It comes on just about in midseason and appears first as watery-looking spots 

 on the fruit. These usually swell and burst open by a crescent-shaped sht, from 

 which there is an exudation of transparent gum that hardens on the surface. In 

 the flesh of such prunes small brown flecks always appear, beneath the gum- 

 spot. These usually consist of a few dead pulp cells situated in the region of the 

 outer network of veins. Such injury is often slight and the prunes mature with 

 very little evidence of the trouble. More severe injury, however, may result in 

 the death of larger areas of the pulp. The resulting collapse of the tissues and 

 cessation of growth produces an irregular or corrugated surf ace. Such affected 

 prunes usually color up prematurely and drop off. 



"In some years, as the prunes approach maturity great losses to growers 

 result from an internal breaking down of the flesh, with brown discoloration and 

 disagreeable odor, which has sometimes been erroneously mistaken for brown 

 rot. This internal browning usually starts immediately around the pit, but often 

 extends outward until in some cases it reaches the skin and involves the whole 

 flesh. The trouble is . . . presumably due to disturbed water balance in 

 the tree and perhaps is similar in origin to 'punk' in the apple." 



The assumption should not be made, however, that all these diseases 

 described and discussed here under the names of cork, fruit-pit, bitter- 

 pit, Jonathan-spot, dieback, rosette, etc. are always due exclusively to 

 disturbed water relations. Though without doubt they often are caused 

 directly or indirectly by excessive moisture or by drought, there are 

 other contributing factors and in some instances their occurrence 

 may be due to these other factors alone. For instance, White ^^^ ^nd 

 Ewert*''' ^^ present evidence that in Australia much of the bitter-pit in the 

 apple is due to localized poisoning caused by the presence of minute 

 quantities of certain mineral toxins absorbed either from the soil or from 

 the coating of certain spray materials on the fruit itself. 



Black-end. — Under the name black-end has been described a physiological 

 disease of pears in which the skin around the apical end of the fruit turns black 

 while the flesh immediately underneath becomes hard and dry and may crack. i° 

 Such fruits are likely to be rounded at the apical end instead of depressed in the 

 usual manner. The blackened area often blends gradually into healthy tissue. 

 This disease is found most frequently in the hotter and drier portions of Oregon , 

 and "all the circumstantial evidence points to the probabiHty that excessive 

 evaporation in hot weather or insufficient soil moisture are responsible for its 

 development, since it appears usually on soils either unfavorable for root 

 growth or unretentive of moisture or both." 



