Gummosis
It sounds like what happens when you eat too many candies, but it’s a serious fungal infection that often affects citrus trees here in Hawai’i. It can affect other trees as well, but I usually see it on citrus. The symptoms generally start with weeping cracks in the bark - thick, sappy gunk can be seen coming from the wounds, reminiscent of amber.
Severe oozing from bark - gummosis infection
Alternatively, gummosis can show up as a dry, peeling wound on the bark of the tree
Gummosis (Phytopthora spp.) is a fungus that is present in most citrus orchards globally, and is usually controlled by the trees themselves (when healthy) and by environment. However, under cool, moist conditions the fungus can really multiply quickly. Note that most orchards experience a hot, dry summer which also controls the quantity of fungus present and active. Here is Hawai’i, that “dry” part is often absent, so this affliction can really take hold of a tree quickly.
The sloughing, peeling bark (whether dry or wet) can girdle a tree quickly and cause death within a year of first noticing the disease, so quick action is recommended.
Though there are plenty of treatment options available, most are not appropriate for organic gardening (and thence, I will not recommend them for any tree grown for edible produce). I generally recommend an old recipe, called a Bordeaux Mix, as a trunk spray and root drench.
Bordeaux Mix is a careful, precisely measured combination of copper sulfate and lime. While those of you who are my customers may frequently see me spraying PPE-free (no gloves, mask, etc), I mask up for this one and will ask anyone else to keep back, especially if it is windy at all. I will mix up one-gallon containers each of lime and copper sulfate, and I will not mix them together until it’s time to apply the mix to the tree.
While gummosis doesn’t directly affect the fruit, it can cause early fruit drop or size distortion due to the systems of the tree that are affected.
References:
Phytophthora Gummosis. (January 2019). Ucanr.Edu. https://ipm.ucanr.edu/agriculture/citrus/phytophthora-gummosis/