Disease identification is facilitated by observation of fruiting structures. Perithecia are found on cortical tissues and will produce globular to sub-cylindrical asci with two-celled ascospores. 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. This suggests that there may be several species or biotypes of "Phomopsis" that cause stem canker worldwide. Pycnidia, the asexual fruiting bodies, can be detected on the stem and leaf lesions throughout the disease cycle. They are embedded in the tissue, dark brown and globular. The conidia come in two types, but the most common is beta conidia that are threadlike, hyaline and can be curled or straight.