It can cause complete crop loss in warm, humid climates, but is virtually unknown in regions with arid summers.”[1] The name comes from the black fringe that borders growing brown patches on the leaves.

[3] In fact, "Viable lesions capable of producing conidia can persist in wood for at least 2 years.

"[4] Spring rains release the ascospores and conidia contained in the overwintering structures and these spores are “spread by wind and rain-splash to infect leaves, blossoms and young fruit”.

[1] In the presence of moisture, these ascospores germinate slowly, taking 36 to 48 hours, but eventually penetrate the young leaves and fruit stems (pedicels).

[6] At the end of the season, the fungus overwinters as pycnidia or pseudothecia within cane lesions or mummified fruit.

[6] When the weather is moist, ascospores are produced and released throughout the entire spring and summer, providing continuous primary infection.

New black rot infections continue into late spring and summer during prolonged periods of warm, rainy weather.

During August, the pycnidia are transformed into an overwintering stage that, in turn, gives rise to pseudothecia within which the spring spores (ascospores) are produced.

"[5] In the spring during wet weather, the "pycnidia on infected tissues absorb water and conidia are squeezed out.

"[5] "Conidia are splashed about randomly by rain and can infect any young tissue in less than 12 hours at temperatures between 20 to 30 °C (60 to 90 °F).

Relatively small, brown circular lesions develop on infected leaves and within a few days tiny black spherical fruiting bodies (pycnidia) protrude from them.

Elongated black lesions on the petiole may eventually girdle these organs, causing the affected leaves to wilt.

Finally, infected berries shrivel and turn into hard black raisin-like bodies that are called mummies.

[1] A mixture of cultural and chemical control practices can manage grape black rot disease caused by Guignardia bidwellii.

Cultural control aspects involve the basics in plant care and field sanitation as well as cleanup after an infectious outbreak.

Remove excess growth, diseased and overwintering berries, leaves, and tendrils from the vineyard, and burn or otherwise destroy them.

Mummies produce spores next to the susceptible grapevine tissues throughout the season; even relatively few can cause significant damage.”[7] Another technique to rid of infection can be to “cultivate the vineyard before bud-break to bury the mummified berries.

Be sure that the conditions are optimal to spray to avoid drift and inefficiencies of the fungicide due to application.

In order to cut down on spraying costs, it is important to understand life cycle of the pathogen.

The most common fungicides that prove to be excellent for certain regions of the United States for controlling black rot are Sovran 50WG, Flint 50WG, Abound Flowable (2.08F), and Pristine 38WDG.

The label states, “Do not use on Concord, Worden, Fredonia, or related varieties due to possible foliar injury.

Experience in New York suggests that Corot noir and Noiret may also be sensitive to Pristine.”[7] Black Rot Control for Organic Growers Excerpt from Dr. Wayne Wilcox’s Grape Disease Notes, 2009 suggests a possible way for controlling black rot on grapes in organic farming.

To try to avoid this, implement a rigorous program to remove mummies during pruning, and spray copper once a week throughout much of the growing season.

This was hard on some of the hybrid vines and runs counter to the thinking of many with a “sustainable” orientation (after all, copper is an element and doesn’t break down into anything else, so it stays in the soil forever), but it did control the disease in an organically acceptable manner.