This disease has been shown to be particularly devastating in southern and eastern regions of Europe, although it can also be found in the United States and Australia.

[2] Sunflower hosts that found in high densities are particularly susceptible to attack by the pathogen due to the microclimate formed in crowded areas.

[3] There has also been recent molecular evidence to suggest there are several genetically distinct species of Phomopsis that can cause disease on the sunflower hosts.

[3] Initial symptoms of P. helianthi infection can be found at the attachment of petiole to the stem on the lower portion of the plant.

[3] Phomopsis stem canker is also characterized by extensive pith degradation to the point where the stalk is easily crushed under moderate thumb pressure.

[3] Phomopsis also produces mycotoxins, which can cause additional symptoms such as premature ripening or early plant death.

It has been observed that isolates from stem canker in the United States will readily form perithecia when grown in culture, but those from Europe will not.

Infection is initiated onto the leaves by windblown or rain splashed ascospores that were released from overwintering perithecia, the telomorphic fruiting body.

[4] The infection begins at lower leaves and spreads through the intercellular spaces and terminal veins throughout the vascular system.

[4] Pycnidia, the anamorphic fruiting body, will form in the infected tissue and release two types of conidia – alpha and beta.

Proper treatment (burning or burying deep under the ground) of the plant waste in fall and crop rotation can decrease disease incidence and severity.

[7] There are several methods that can be employed to control this disease, some of which are discussed below: In early 1980s all the commercial hybrids available were completely susceptible.

In 2010, Debaeke and Moinard showed that the early Phomopsis attacks were related to changes in microclimate resulting from crop management practice or cultivar architecture.

The later attacks were more dependent on surface area of leaf available and air movement in the canopy provided the inoculum is present and microclimate is favorable to germination of spores.

Emergence of this new disease became more and more apparent with increased number of reports from all over the world including Rumania in 1985, Hungary in 1983, France in 1985, and Iran in 1988.