A Bacterial Disease of Stone Fruits 383 



Michigan, Nebraska, and Texas. Diseased material has been obtained 

 by the writer from Alabama, Arkansas, Florida, Georgia, Illinois, Iowa, 

 Kansas, Michigan, Missouri, New Jersey, New York, Ohio, Oklahoma, 

 Pennsylvania, South Carolina, Tennessee, and Texas. 



ECONOMIC IMPORTANCE 



Bacterial leaf spot, or shot-hole as it is usually called, is one of the chief 

 foliage diseases of stone fruits in the humid districts of the South. It 

 occasionally becomes more or less aggressive also in some sections of the 

 northern and eastern States. Its importance varies from year to year, 

 there being an abundance in wet seasons and little in dry seasons. The 

 disease appears to be more severe in warm, humid regions than in cool, 

 dry sections. In southern Missouri its economic importance has kept 

 pace with the growth of the peach industry, and it is now one of the most 

 difficult diseases with which the fruit grower has to contend. Its attacks 

 on the plum have made it practically impossible to grow certain varieties 

 of Japanese plums on a commercial scale. The fruit of some varieties of 

 apricot and nectarine also are injured more or less by the disease, but 

 since apricots and nectarines are not extensively grown in Missouri the 

 disease on these fruits has not attracted much attention. 



In different parts of Missouri, during 1908 and 1909, a record was 

 made of the amount of infected fruit in diseased Elberta peach orchards, 

 in order to determine the extent of the injury due to this disease. It 

 was found that from 1 to 10 per cent of the fruit was infected in orchards 

 well cared for, and from 25 to 75 per cent in orchards poorly cared for. 

 The lesions on the fruit are in many cases not sufficiently prominent 

 to mar its appearance greatly, but the larger proportion of such fruit 

 is graded as " seconds." None of the fruit holds up well in shipping, 

 and in some cases it is completely destroyed by various rot-producing 

 organisms before being placed on the market. 



It is especially difficult to obtain reliable figures on the loss due to this 

 disease, since the loss is not confined to the direct effect on the fruit but 

 must include also the influence of the diseased foliage on the general vigor 

 of the tree. Severe outbreaks soon impair the efficiency of the foliage, 

 and if they occur early in the season they reduce the size and greatly 

 lower the quality of the fruit. Severe foliage injury also has a marked 

 influence on the formation of fruit buds, and trees that have their leaves 



