Leaf Drop

• The Michigan State University Extension explains that cherry trees, Yoshino cherry included, are susceptible to the Xanthomonas pruni bacterium, which causes a condition called bacterial spot. Coccomyces hiemalis is a fungus that causes leaf spot. Both cause small spots that dry and open to develop. The leaves eventually drop from the tree.
  
  

Help From Fungicides

• Fungicide applications will help keep your Yoshino cherry from developing fungal leaf spot. Applications begin just after blossoms lose their petals, and continue every seven to 10 days through the summer.
  
  

Keep Things Clean

• The organisms that cause leaf drop in Yoshino cherry stay on the diseased leaves that fall to the ground. Rake these up and throw them in the trash. Keeping your Yoshino cherry tree healthy also means pruning it to assure good air circulation.
  
  

Other Leaf Problems

• Powdery mildew can also occur on Yoshino cherry tree leaves. It casts a whitish film on plant leaves and causes disfigurement. Powdery mildew can be controlled with fungicides.
  
  

Pests of the Yoshino Cherry

• The University of Florida IFAS Extension reports that insects such as aphids, tent caterpillars, borers, spider mites and scales can attack Yoshino cherry trees. Attacks from insects can weaken a tree and make it more susceptible to disease.