Apple Scab Disease on Crabapples and Apple Trees
WHAT YOU’LL SEE…are dark olive colored spots on both sides of the leaves. In moist weather, the spots may take on a felty appearance due to fungal mycelium growth. Occurrence of the fungus will occur in the spring at the time of, or just after leaf break.
THE REASON FOR THE PROBLEM…is an over-wintering fungus on fallen leaves. If the leaves are not cleaned up and disposed of, the fungus infects the new emerging leaves. The fungus also can be carried by the wind from other areas of the yard and neighborhood.
THE BEST WAYS TO CONTROL THIS PROBLEM…is to plant resistant varieties of trees. But since your tree is already planted, the next best thing is to be sure all fallen leaves are cleaned up and disposed of each fall. While you have no control over what may blow in from neighboring areas, at least be sure the area immediately surrounding your crabapple is clean.
OTHER OPTIONS AVAILABLE TO YOU…include protective fungicide applications. The first application should occur just after the leaves appear, with two or three additional applications following during the summer. While good control of this fungus can be achieved, total eradication of the disease with fungicide applications is not realistic.
Fire Blight Disease on Crabapple and Apple Trees
WHAT YOU’LL SEE…is that the young shoots appear dead and burnt. Many young branches will bend and resemble an upside down “J”, a common symptom of this disease. Others will simply appear brown at the terminal end of the branch.
THE REASON FOR THE PROBLEM…is a bacterial disease. The fact that it is a bacterium and not a fungal disease makes it very different than the majority of ornamental problems. Fireblight will progress into the older wood and causes cankers (open sores) which is where the disease over-winters. Susceptible plants can be killed over a period of three – five years due to the severity of this disease.
THE BEST WAYS TO CONTROL THIS PROBLEM…is to remove and destroy all infected branches and twigs. It is best to actually burn the branches, if possible. Prune the tree in dry weather and disinfect the pruners after each cut with a 10% bleach mixture.
OTHER OPTIONS AVAILABLE TO YOU…include fall deep root fertilization of the tree. Maintaining the best plant health possible, without a burst of growth in the spring will help prolong the life of the tree.