According to WebMD www.webmd.com trees can be affected by diseases http://www.webmd.com/allergies/tree-pollen-allergy WebMD trees can be affected by diseases http://www.webmd.com/allergies/tree-pollen-allergy http://www.webmd.com/allergies/tree-pollen-allergy http://www.webmd.com/allergies/tree-pollen-allergy trees can be affected by diseases trees can be affected by diseases