This can cause the leaf to curl as well as premature defoliation (more common where disease is more severe) upwards of 85%.

The upper epidermal cells appear to remain relatively normal as well, as hyphal growth goes below this layer.

Healthy epidermal cells contain a large central vacuole surrounded by a thin cytoplasmic layer with endoplasmic reticulum, chloroplasts with well-developed grana, starch granules, and osmophilic globules.

Nuclei are enlarged, plus a 2-3 fold increase in the number of organelles normally present in these cell types.

These alterations indicate intense metabolic activity, appearing to dedifferentiate and resemble meristematic cells.

[9] Concave depressions with asci in them on the top and bottom of leaves suggests direct penetration.

Infection triggers hyperplasia and hypertrophy, likely due to the production and excretion of a hormones called cytokines[8] produced by Taphrina species, and other symptoms as described above.

With no special mechanism, ascospores are all forcibly discharged from the ascus to sit on the leaf surface.

Blastospores and conidia bud directly, with a noticeable constriction point, from these ascospores while in the ascus as well as after they have discharged.

Extending hyphae are long and thin, sometimes branch, and in an appressed manner appear to follow the leaf contours in growth.

These hyphae grow over guard cells and enter the leaf tissue through open stomata.

In the saprophytic stage the single celled spores grow like yeast, that is to say they bud (replicate) directly.

[14] Management recommendations for oak leaf blister is primarily to focus on mitigating other stressors to the tree.

[15] Sanitation methods such as removing fallen leaves in autumn can reduce disease inoculum for the following spring [16] Fungicide application is not a necessary management strategy because T. caerulescens does not severely harm plant health and is considered a purely cosmetic disease.

If, in rare cases, the disease is severe, fungicides can be applied in spring before the tree buds.

Once the spores have infected the young bud tissue in spring it will be too late to reduce disease by fungicide treatment.

[17][21] Oak leaf blister is not considered a significant threat to tree health and is a cosmetic disease.

Although the disease causes very little damage to plant health, it is important because it is found throughout the United States.