Summer diseases can damage the farmstead forest. Some of these issues can be detrimental to trees and shrubs over the long term, while others are purely cosmetic. Recognizing the symptoms and signs of tree problems can help you assess and maintain the health of your trees. Keeping that in mind, it is always best to consult your local certified arborist or Extension forestry specialist to positively confirm the existence of specific diseases or environmental stresses. I’ve used the expertise of University of Minnesota research fellow Eric North to help fill in the details as I developed a general farmstead tree disease watch list. Here is a brief summary of five diseases that made the list.

CHLOROSIS: Iron chlorosis in pin oak trees is one of several tree diseases and issues that can plague farm trees throughout the summer and early fall. (Photo: Eric North, University of Minnesota)

Wilts. These can kill a tree in a short period of time or over a matter of years. Wilt diseases infect tissue inside the tree and roots, so positive identification is challenging. The bad news is that wilt disease is often fatal to the tree. Wilting could be caused simply by drought or underwatering — but if the disease exists, the tree may not recover. The best way to control wilts is to plant resistant varieties, but there are also several wilts that can be managed with preventative fungicide injections, North says.

Leaf spots. A common fungal disease, these issues are often only cosmetic and not detrimental to the long-term health of a tree. The later in the season the tree develops leaf spot, the less reason there is for concern. Anthracnose can be severe in sycamores, causing twig dieback, and in some cases complete defoliation. But generally, the tree will recover without long-term harm. Wet conditions promote these issues, so avoiding lawn or garden irrigation over the tree canopy and not overcrowding trees will assist in prevention. Pruning to increase light penetration and improve air circulation around the trees will also help.

Apple scab. Another fungal spot disease, apple scab results in apple trees dropping leaves by late summer, and it can cause blemishes on apples. Scab can be controlled by planting resistant varieties. Early-season fungicide treatments can prevent the disease on trees where leaf spot has not already appeared.

Cedar apple rust. This is an alternate host disease that hits apples and crabapples. A similar Gymnosporangium rust strikes quince and hawthorns. These rusts are considered leaf spot and cause more visual damage than anything. They can be controlled by planting resistant varieties, by pruning or removing infected twigs, or by applying protective fungicides before infection occurs. According to North, the fungus needs a juniper or cedar in order to complete the life cycle, so you could manage the disease by removing junipers or cedars adjacent to the apple trees, or refraining from planting them near susceptible trees.

Iron chlorosis. Pin oaks are well-known for this common issue because they react to highly alkaline soils. The trees aren’t able to take up enough iron, so newer leaves at the branch tips turn yellow while the leaf veins remain green. This is a severe issue that will often shorten the life of the tree if not corrected. There are treatments for established trees, like foliar iron or manganese, and trunk injections or implantations and soil fertilizer applications. These should be conducted by a certified arborist. North points out, however, that there are cultivars that have been specifically created to produce yellow leaves.

You can learn more about tree diseases to watch for on your farm by contacting your state forestry specialist.