I planted a sweet gum tree about 4 years ago. In the summer the leaves on the upper portion go black and it defoliates the upper portion. My neighbor has the same problem with their sweet gum. Have any solutions?
Hardiness Zone: 7a
Lance from Touchet, WA
When any part of a tree goes black, it indicates too much moisture which gives way to wilt, disease, pests, decay or death. If it is just the top, and happening to the neighbor's tree as well, it sounds like you may live over a shallow water table, an old rice paddy-like area, or there is draining water towards those two areas from higher ground. It's going to be difficult to help the trees which may also have reached soft chalky rock as the center tap roots grow deeper. It's not likely that they get too little moisture.
You should join efforts and funds and call an arborist for an opinion as to whether or not the two trees can be saved or if there is a fungicide solution that can be injected deeply into the ground to the deepest roots. Unfortunately the tops may have to be cut out which may ruin the shape of the trees, but may save their life.
Check the elevation of your ground. Even a slight low area around the trees can cause water run-off to puddle and cause trouble for the trees. Make certain there is no mulch around the base of the main trunk, that there is nothing being sprayed in the area that could have drifted to the tops of the trees, including pollution from any nearby highways or crop dusting from the air. Also, call your local agricultural extension district to inquire as to what they might know it could be and any other suggestions as to how to treat the problem.
If it is a drainage issue, I'd dig a 6" wide x 8-10" deep trench around the trees at about 3-4' from the main trunk. Line the trench with shade cloth and carefully overlap seam and top edges to hold filling. Slowly fill the trench with 3" of crushed charcoal, topped with 4" shattered shale or medium gravel, and then top the gravel or shale with larger gravel or washed river rock/stones to bring level with soil, not grass. This is one method of creating a drainage away from the trunk and deepest roots that should catch rain run-off before it puddles at the base of the trees.
Should you fertilize the trees with the proper foods, do so in the trench area for better distribution, but sprinkling lightly as the drip-line grows wider from the main trunk. While checking for other causes, remember to consider local high power line emissions, or paint from some source nearby. Also inquire of the oldest neighbors as to whether or not your lots were the last to be built on. If so, like mine, they may have been the "dump" for all construction and has god only knows what all beneath the soil beneath the trees.
The very last thing to consider is borers, but it's not likely for just the tops of the sweet gum trees. I have read of some pests that attack just the tops of trees, now that I think harder about it. God bless and help you. : )
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