6 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 50 



wounds. This exuding of sap is commonly called fluxing. The 

 other symptoms (yellowing, scorching, and wilting of leaves, dy- 

 ing of branches, and general decline of the entire tree) may de- 

 velop when the sap spreads to current-season wood and is trans- 

 ported in the sap stream. 



Abnormally high pressures caused by fermentation force the 

 accumulated sap and gas out of the trunk through cracks in 

 crotches (Fig. 4), through wounds made by removal of branches 

 (Fig. 5), through cracks in trunks (Fig. 6), and through other 



Fig. .5. — Wounds that result 

 when branches are removed 

 frequently show abundant flux- 

 injj. Air-borne bacteria, yeasts, 

 and other fungi may grow in 

 fluxing sap and produce gray- 

 brown, foamlike, ill-smelling, 

 slimy masses called slime flux. 



trunk injuries (Fig. 7). The sap or flux is colorless to tan as it 

 oozes out of diseased wood but it turns dark upon exposure to air. 

 When abundant oozing occurs, the flux flows down the trunk, 

 wetting and soaking large areas of bark. As the flux dries, it 

 leaves a light gray to white incrustation on the bark (Fig. 8). 

 Fluxing may occur from April to December. However, it is most 

 conspicuous during July, August, and September, when the wet- 

 wood organism is most actively fermenting sap and producing 

 abnormal pressures in the diseased wood. Temperatures are opti- 

 mum for rapid growth of the wetwood bacterium during these 

 months. Fluxing usually ceases during January, February, and 

 March. During these months, the wounds through which fer- 

 mented sap has flowed can be detected by the gray to white in- 

 crustation of dry flux on the bark. 



The exuding wetwood flux is suflRciently toxic to retard or 

 prevent callus formation. It frequently kills the cambium at the 



