The cool, wet spring makes it not only difficult to mow your lawn and plant your garden, but it can also have a crippling effect on the success of hardwood regeneration, particularly black cherry. Over the past several years, foresters through the Allegheny Plateau have noticed the “lack” of black cherry regeneration in predominantly Allegheny Hardwoods stands (black cherry dominated). Many times, the lack of regeneration can be result of too much competing vegetation (birch, beech, grass, etc.).
Over the past several years, cooler & wetter than normal springtime weather has seem to be the new norm. Foresters and researchers are starting to correlate that the weather & a fungal disease may be a real reason for the lack of black cherry regeneration. Cool, wet weather typically causes fungi to be more prevalent, and the particular fungus, “cherry leaf spot” is caused by the fungus Blumeriella jaapii. The fungus overwinters in leaf litter on the ground and then spreads in the spring via spores to freshly leafed out cherry trees and seedlings.
Foresters typically notice the leaf spot showing up in late June. This year, leaf spot was found to be prevalent on black cherry seedlings the first part of June. Typically, first year seedlings show symptoms first, as the leaves to do not have the developed waxy coating to protect them. Leaf spot usually leads to mortality of the leaf, which occurs typically in July and August. Overstory black cherry trees also develop leaf spot, but typically that occurs later in the summer and can also lead to early leaf fall.
When leaf spot occurs on first year black cherry seedlings, mortality of the seedling usually occurs. As a seedling develops and matures, its ability to withstand leaf spot is increased. Overstory trees usually can withstand a leaf spot outbreak, as defoliation usually occurs later in the summer when most of the tree’s growth has occurred. Recently, researchers and foresters are noticing that the increase in leafspot may be causing reduced annual tree growth, and may be leading to poor seed development and minimal seed being produced.
So what’s the solution? Cherry orchards typically spray fungicide to control the leaf spot fungus. From a forest management standpoint, spraying fungicide is generally not economically feasible and also requires many repeated applications throughout the growing season. Researchers and foresters are focusing on options such as fertilizing or soil chemistry to find alternative options that may work better. Recently while conducting regeneration evaluations, Forest Investment Associates and FORECON foresters noticed that cherry seedlings that were covered by grass or brush seemed to show less symptoms of leaf spot than those seedlings that were not under any cover. In addition, seedlings under hemlock seemed to look much healthier, which may lead to the fact the soils are more acidic under pine and there is less prevalence of cherry leaf spot as the overstory cherry tree is not directly over the seedlings.
In past years, many areas that were predominately black cherry overstory usually had a significant portion of black cherry regeneration present with minimal leaf spot. Many young pole stands dominated by black cherry today were a direct result of very successful forest management and black cherry regeneration establishment in the past. Today’s challenges involve finding ways to hopefully continue to ensure the “best black cherry in the world” is present in future woodlots. For more information regarding cherry leaf spot visit Penn State Extension’s website at: https://extension.psu.edu/cherry-disease-cherry-leaf-spot or contact FORECON at 716-664-5602 or fill out a request at www.foreconinc.com.