Daylight savings, melted snow, brown grass turning green, tree buds swelling—these are all wonderful signs that spring is (hopefully) here. As the temperature in Michigan slowly begins to increase, the time approaches to discourage pruning oak (Quercus) trees. The Michigan Department of Natural Resources recommends avoiding oak pruning between April 15th and July 15th. Although wounding in oaks may be accidental such as severe storms breaking branches or animals scratching or pecking into the bark, oak wilt is most preventable if pruning ceases in spring and summertime.
Michigan climate does indeed vary greatly. Therefore, why between the dates April 15th through July 15th should oak trees remain undisturbed? It is not solely the wounding that makes the tree susceptible to oak wilt, it is the beetles that feed on the oak sap and transmit oak wilt fungal spores from an infected tree to a healthy tree. Mid-April is generally when the beetles become active and they remain active until mid-to-late summer, around July 15th. Although these dates are arbitrary, it does remind us that during this time of year oak trees are most susceptible to become infected with the oak wilt fungus. We recommend if you are going to use these dates, prune or trim your oaks either much earlier than mid-April or much later than mid-July to ensure beetles are not still active. If you’re ever skeptical about whether it is a proper time of year to trim your oaks, give us a call. We are more than willing to you determine whether the time of year is right. After all, once an oak (depending on the type of oak) is infected with oak wilt, unless treated immediately, it is likely to die within a few months to a few weeks.
Not all oak trees are extremely susceptible to oak wilt. While red oaks are extremely susceptible to oak wilt, white oak trees are much more resistant. If you’re thinking of planting oak trees on your property, depending on your soil type and landscape environment, we strongly recommend planting white oak trees since you will have a better chance of having oak trees with long lives. For some reason unknown to scientists, the oak wilt disease progresses much more slowly in white oaks than it does in red oaks. Simple clues in identifying what type of oak tree you have are red oaks have pointed lobes and white oaks have rounded lobes. If you need assistance in identifying your oak tree, please send pictures of the oak leaf, bud, twig, bark and whole tree to KimB@integritytree.com along with your name and phone number.
If you have any questions about the oak wilt disease in Michigan or if you would like to know more, call us or visit the Michigan Department of Natural Resources webpage. Oak trees have more of a chance by prevention of infection and a part of prevention is sharing knowledge about oak wilt.