Question
i recently fertilized the lawn twice because our female dogs were burning lawn;  leaves were fine on willow then one day they dried up and fell;  i can see some slight green coming thru; did the fertilizer hurt the willow

Answer
If the fertilizer was one called Weed and Feed it can harm trees. These type fertilizers contain a herbicide that will damage trees and should not be used on lawns with trees. Use a liquid lawn herbicide rather than a granular one. Normal fertilizer with out the herbicide will not harm the tree. Dog urine next to the tree can cause the tree to yellow. If the tree is budding out new leaves it should be ok. You may lose some of its fullness but it should recover.