Guignardia bidwellii

Guignardia bidwellii is a fungal pathogen that causes a disease known as black rot in grapes. It is a member of the Ascomycota division, which includes a wide variety of important plant pathogens.

Taxonomy

The fungus was first described by Pierre-Athanase Guignard, a French botanist, and was later named in honor of him and American botanist John Bidwell. The scientific name Guignardia bidwellii reflects this history.

Description

Guignardia bidwellii is a necrotrophic fungus, meaning it kills host tissue and then feeds on the dead material. It produces small, black, spherical fruiting bodies known as pycnidia. These structures contain spores that are spread by wind and rain to new host plants.

Disease Cycle

The disease cycle of Guignardia bidwellii begins when spores are released from pycnidia and spread to grape leaves, stems, or fruit. The spores germinate and penetrate the plant tissue, causing necrosis. The fungus then produces new pycnidia on the dead tissue, completing the cycle.

Management

Management of Guignardia bidwellii involves a combination of cultural practices and chemical control. Cultural practices include pruning and training vines to improve air circulation and reduce leaf wetness, which can promote fungal growth. Chemical control typically involves the use of fungicides.

Impact

Guignardia bidwellii is a significant pathogen of grapes, particularly in regions with warm, humid climates. The disease can cause significant yield losses and reduce the quality of the fruit.