Question
Greetings,
 My parents live in Monument, Colorado. They have a cherry tree and the problem is that the leaves grow slinder finger-like growths on the leaves and the leaf that is affected also curls up, dries up. Fungus? Neematodes? These growths dangle from the leaves. Fruit is unaffected, but it looks horible. Do you know what this is?

Kind Regards,
Royce Faina

Answer
These are Cherry pouch galls
Cherry Pouch Galls
A mite forms cherry pouch galls, fingerlike projections on top of cherry tree leaves. These numerous galls usually grow in spring as the leaves grow. Their presence is a sign of mites feeding and breeding. Anyone looking at cherry leaves during the summer might notice them. They don't occur on all cherry trees, but they are abundant when present. They drop with the leaves, and the tree appears to have never been visited by these gall makers.

Galls are abnormal growths that plant tissue develops in response to insect feeding, saliva, or egg-laying. They are rarely harmful, and should be seen as biological curiosities. The mites lay eggs on the leaves and secrete a chemical that causes the leaf cells to expand over the eggs. Eggs hatch and the young feed inside the pouch. These types of damage are more aesthetically objectionable than detrimental to overall plant health and vigor. Nurseries control these on small plants they ares selling but on larger plants in yards most are not treated. To use a spray one would need to treat the adults before they lay the eggs and this is a narrow window. You could use a soil applied systemic insecticide that the plant roots pick up and take to the leaves protecting them from attack. But this is a one time occurrence per year and chances are next year there will be be signs of the galls. Since they do not harm the tree except make small spots on the leaf I would just enjoy them as a unusual occurrence.