Common spot of strawberry is caused by the fungus Mycosphaerella fragariae (imperfect stage is Ramularia tulasnei).

[2] This disease affects strawberry plant foliage causing purple spots 1⁄8 to 1⁄4 in (3.2 to 6.4 mm) in diameter across on the upper side of the leaves.

[7] The disease cycle starts when the pathogen overwinters as mycelium or fruiting structures in leaf debris and spores are spread by rain splash infecting new leaves as they emerge in the spring when conditions are favorable.

[6] Common spot on strawberry is a polycyclic disease, and under favorable conditions it will continue to reinfect the host and surrounding plants.

Older infected leaves that remain alive during winter may give rise to conidia that are spread to new foliage by splashing water or human contamination.

[3] Another type of spore (ascospore) is generated in speck-sized black perithecia, which are produced at the edges of the leaf spots during autumn.

About 4–6 weeks later, it is generally a good time to apply another application of nitrogen fertilization to the developing strawberry plants.

[13] Under favorable environmental conditions, this disease can cause serious reductions in strawberry yields,[14] which would definitely be a problem for commercial growers.

Although the disease will not completely kill the plants, several leaves will be destroyed and poor quality strawberries will be produced as a result.

[3] Chart 1 shows that leafspot (also known as common spot of strawberry) has a 4 out of 5 rating in terms of occurrence and yield loss.