Question
I live in the south of France and have two mature Mulberry trees,about 12ft apart. With one the leaves turn brown and yellow and drop in the middle of summer as if it was autunm.The bark on some branches have split badly and breaking away from the branch. The other tree is quite healthy apart from one branch which is bleeding badly close to the trunk.I did prune it back but is still bleeding.Can you suggest what I can do.

Answer
Hi there:
1.It sounds like the leaves have a disease called leaf spot. During moist seasons the fungi will grow and cause spots on the leaves and could if conditions are good for the fungi growth (moist) cause the leaf to die. This normally will not kill the tree but will reduce the
growth and fruiting. Here in the USA we have had an abundance of rain fall this spring/ summer and have a large "crop" of leaf spots on the  hardwood tree leaves.Nothing you really can do on large trees and as long as the tree has green leaves I would not be too concerned.

2.The bark sloughing off is common on old mulberries. Also as the trees get older the weight on the ends of the limbs will cause cracking.

3.WETWOOD:

Wetwood is a bacterial disease.The infection can be in a wound on the trunk surface or it can be deeper inside the trunk. In either case, bacteria ferment the tree's sap; it seeps out and down to the ground. Sweet-eating insects (wasps, bees, yellow jackets) would obviously be attracted to the damaged area. The infected wood is frequently discolored or appears water soaked (wet wood).

Gas (carbon dioxide) is produced by fermentation by bacteria. The gas produces pressure in the wood. This pressure forces sap from the trunk through cracks in branch crotch unions, pruning wounds, lawn mower wounds, other injuries and occasionally unwounded bark.

This oozing is called "slime flux" and is caused by a bacterial infection inside the trunk.There are actually two types of slime flux: alcoholicand acidic. The acidic flux smells like vinegar. The flux is colorless to tan at first but darkens up with exposure to the air. As fluxing continues,large areas of the bark become soaked. Many different microorganisms grow in the flux producing a foul or alcoholic smell. Various types of insects are attracted to the slime flux. If the fluxing continues for months, leaves on affected branches may be stunted and chlorotic.

Grass may be killed where the flux runs down the trunk onto the grass.The flow of sap is periodic; it may disappear and not reoccur or you may see it every year.

Sap may continue to ooze for several weeks or months, but usually it eventually stops with no treatment and no apparent damage to the tree. This slime flux may be triggered by heat, drought and other stress.

There is no treatment for the condition. The best thing to do is to wash off the trunk to discourage bugs. Mix a pint of chlorine bleach in a gallon of water to make a final rinse. Try to maintain trees in a general good state of vigor and minimize wounds and injuries.

More damage can be done to the tree in attempting to cure wetwood than the flux will do alone.

Hope this helps,Bill