CARTER: THE WETWOOD DISEASE OF ELM 5 



abundance of potassium. These elements appear to be present in 

 the sap as carbonates. The sap and water extract from the 

 affected wood of a diseased elm are alkaline, while water extract 

 from healthy sapwood and heartwood of normal elms is acid in 

 reaction. The wetwood sap has a pH of 7.11 to 8.55, and the water 

 extract from wetwood-affected wood has a pH of 7.06 to 7.80. The 

 water extract from healthy wood has a pH of 6.11 to 6.60. 



External Manifestations 



An elm affected by wetwood may show one or more unsightly 

 or detrimental external manifestations of the internal infection. 

 These external manifestations or symptoms include the exuding 

 of fermented sap through wounds, yellowing of foliage (followed 

 by premature defoliation), scorch of foliage, wilting of foliage, 

 dying back of branches with wilted foliage, and general decline 

 of the entire tree. 



Flux. — The most conspicuous symptom of wetwood in a tree 

 is the bleeding or exuding of fermented sap through trunk 



Fig. .3 iU'ft). — Abnormal pressures develop in the diseased wood <»!' elms 

 and other trees alTeeted with wetwood. Many afi'ected trees that do not flux 

 have unusually high pressures, as shown in this picture. 



V\<i- 1 (rif/lii). — Bleeding or fluxiu};; through wounds, such as cracks in 

 crotches, is the most common external e% idence of wetwood in elm. 



