A GUM-INDUCING DIPLODIA OF PEACH 

 AND ORANGE 



H. S. Fawcett and O. F. Burger 



A species of Diplodia has been isolated in pure cultures from 

 both peach trees and orange trees in Florida, and by inoculation 

 tests has been shown to produce copious gumming on healthy 

 individuals of these hosts. 



This species was first obtained from the interior of gumming 

 peach branches on July 14, 1910; and the usual methods were 

 employed to secure pure cultures free from possible bacteria or 

 associated fungi. The same fungus was afterwards isolated from 

 specimens of gumming peach branches from five different locali- 

 ties in five counties of Florida. The two most widely separated 

 localities were West Tampa and Pensacola, about 350 miles apart. 

 A fungus which appears identical with this was isolated from 

 gumming orange branches on September 3, 1910, and it has since 

 been isolated from diseased orange limbs and decaying orange 

 fruits from ten different localities, in six counties. 



In all, ten series of inoculations covering a period of five months 

 have been made on peach and orange trees ; five series by intro- 

 ducing pure cultures of the Diplodia isolated from the peach into 

 peach trees ; three series by introducing pure cultures, isolated 

 from orange, into orange trees ; and two series of cross inocula- 

 tions by introducing the peach Diplodia into orange trees and the 

 citrus Diplodia into peach trees. The peach trees used for these 

 inoculations were about two years old, and the orange trees one 

 to three years old. They were growing in pots in the greenhouse. 

 In most of these inoculations the bark was cut through with a 

 sharp scalpel, a bit of fungus mycelium inserted, and the inocu- 

 lated portion wrapped in oiled paper and tied with raffia. A few 

 inoculations were made without cutting the bark. Check trees, 

 cut and wrapped in the same way, but not inoculated, were kept 

 in every case. 



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