Hello,

Apple anthracnose, also known as “Bull’s-eye rot,” is a fungal disease that can cause significant damage to apple trees. It manifests as cankers on the bark and can lead to a post-harvest fruit rot1. The infection generally occurs during fall rains and is most visible when the bark is moist. As the lesions enlarge, they become sunken and turn an orange-to-brown color, with a margin developing between healthy and necrotic tissue, causing the bark to crack around the infected area.

The round-headed apple borer is a different issue. Borers are insects that can create holes in the wood of apple trees as they tunnel into the trunk and branches. While cankers might not directly cause a borer infestation, damaged or weakened trees, including borers, are more susceptible to pests. The cankers can provide entry points for borers and other pests, potentially correlating the two problems.

Management of apple anthracnose relies heavily on pruning out the cankers to remove the source of inoculum. Trees that are heavily infected should be removed from the orchard and burned. Chemical controls are also necessary, as fungicides are needed in conjunction with pruning to manage the disease effectively. However, no systemic pesticides currently will control the disease, so it’s essential to refer to local extension services or plant disease management handbooks for specific pesticide recommendations1.

For the round-headed apple borer, management typically involves physically removing the larvae and protecting the tree trunks with guards or white latex paint to prevent the adult beetles from laying eggs on the bark. It’s also crucial to maintain tree health to make them less attractive to borers.

In summary, while there may not be a direct causation between cankers and borers, there is a potential correlation due to the increased vulnerability of stressed trees. It’s essential to address both issues promptly to prevent further damage to your apple trees. Consulting with MSU Plant & Pest Diagnostics Lab can provide region-specific advice and management strategies.

For a confirmed and precise identification of the problem, I recommend you send all your images by e-mail to the MSU Plant & Pest Diagnostics Lab. The experts there can also provide you with the best treatment options. Their email is <personal data hidden>. Please include your name. The lab will let you know if they need a sample sent. FYI, the lab may also ask for additional images.

Their website is at this link:

Plant & Pest Diagnostics (msu.edu)

Their Contact Information is at this link:

Contact Us - Plant & Pest Diagnostics (msu.edu)

This link will explain the details of submitting a sample to MSU Plant & Pest Diagnostics Lab:

Submit Samples - Plant & Pest Diagnostics (msu.edu) 

I hope this helps