Question
weeping mullberry fungus problem what conditions creat the fungi problem is it over watering or some other condition.

Answer
It sounds like your mulberry has a common leaf spot that attacks mulberry.  This fungus survives the winter on fallen leaves, so it is critical that you rake up and discard the dropped leaves.  Do not compost since sometimes the composting process does not kill all the fungal spores.  

If you do not remove all the dropped leaves, the fungus can infect new leaves in the spring.  This usually occurs following a rain.  The spores are discharged from fruiting bodies and will splash or be blown to the young leaves.  You may notice small spots a few weeks later if conditions are favorable (moist and not too hot).  These spots will produce a different type of spores which infect nearby leaves when the spores are splashed or blown.  Often the disease will not progress during hot and dry summer weather.  In the fall, when cooler weather and heavy dews return, the fungus reactivates and new leaves will show spots and turn yellow.

If you want to use fungicides to control the disease, the products available are protectant fungicides.  That means that they must be present on the leaves before the disease starts.  They will only provide where they are sprayed, so reapplication may be needed if the tree is vigorously growing and putting on new leaves.  It is best to start applications in early spring just as leaves are unfolding. Two or three applications 7-14 days apart may be needed, especially if you are experiencing a rainy spring.

Products available for control of leaf spot of mulberry will vary depending on the garden center.  You can select chlorothalonil (Daconil, Bravo), fixed coppers (copper sulfate, copper hydroxide), mancozeb, maneb, or zineb.  Follow the label directions for mixing and applying the fungicide.

You may also want to take a look at trees in a wooded areas that are near your home.  If the leaf spot problem continues and does not get better with fungicides, more spores may be coming in from a nearby source.  You may find mulberry trees in neighbors' yards or wooded areas that are affected by the problem and could be a source of spores.

Good luck with your trees.