Blossom wilt is a fungal disease of trees, especially fruit trees, caused by the fungi Monilinia laxa and M. fructigena. The two fungi are very closely related and indistinguishable to the naked eye. M. laxa more commonly causes blossom wilt on pears and stone fruit, and a specific form, M. laxa f. sp. mali is restricted to apples. M. fructigena more commonly causes the disease known as brown rot in the fruit.
Many top fruit are affected, including apples, pears, plums, cherries, nectarines, peaches, apricots, and ornamental varieties.
The damage begins at flowering time in mid-spring, but becomes more obvious as shoots die back in late spring and early summer.