Our Aspen are weeping a brown sap. A web site said the condition is terminal. A local weed and feed company said the condition can be treated with an antibiotic for pigs. Do you have information on the best treatment?
It sounds like your tree is suffering from a bacterial disease called Slime Flux. According to "The Ortho Problem Solver" (AKA the Big Book of Bugs), the bacteria in question is Erwinia nimipressuralis. Here's more of what Ortho has to say (emphasis mine):
The bacteria affect the heartwood, producing abnormally high sap pressure. The pressure... forces the fermented sap, or flux, out of the wounds, cracks, or crotches of the tree. Flux is especially copious when the tree is growing rapidly. Large areas of the bark may be coated with the smelly, bacteria-laden sap, which dries to a grayish-white color. In addition, wounds do not heal, and the bark is unsightly. A tree with this problem is often under water stress... The problem may persist for many years.
The entry goes on to say that "There are no controls for this condition." Because this is a bacterial issue, it is possible for you to pass the bacteria to other trees if you prune this tree and then prune other trees with the same non-sterilized tools.
Note the part about the water stress - has your area been in drought conditions recently? If so, have you watered the tree? How much per week?
I once owned an American elm that suffered from slime flux for at least five years. Eventually it went away by itself, possibly because I removed competition for water (I took out a ton of nearby invasive shrubs).
I can't really see how anyone can get an antibiotic into the heart of this tree without damaging it - certainly, not someone from a weed-and-feed company.
For professional results you should contact a professional - in this case, a certified arborist.