Question
I have a globe willow tree appx. 15 yrs old has started oozing a white foamy substance. it started at the bottom of the tree and has worked its way up to the limbs? what can I do for this>

Answer
This is called slime flux caused by a bacteria. The bacteria builds up in the tree and the pressure pushes the ooze out at a weak point on the trunk. The is nothing that can be done to combat  this bacteria except to improve the health of the tree by fertilizing and water. Fertilize the tree with 10-10-10 fertilizer at the rate of 1 lb per inch of trunk diameter scattered around the tree and watered in good. The water the tree once a week with 1 inch of water (place a pan under the tree and turn the sprinkler on and when the pan has 1 inch of water in it stop). This will deep water the tree.
Over time the oozing will stop.