Elm tree disease
What kind of fungi is it? (Attached the image). Is there any treatment for it? Thank you for the answers
It's hard to see from the photo if it is powdery mildew (a fungal disease), or maybe giant white fly (an insect pest that puts out a cottony mass for self protection). If it's white fly you will see some white, winged fying insects in and about the white material.
If its' a large elm tree you will need to hire a tree service or pest control service with spray equipment. If it's small you can use 70% need oil sprayed every week until the problem clears up.
A tree or pest control service may use a more specific fungicide or insecticide for spraying or injecting, depending on their diagnosis.