Elsinoë ampelina is a plant pathogen, which is the causal agent of anthracnose on grape.
This type of anthracnose affects several plant varieties, including some brambles and wine grapes. Grape anthracnose can be identified by the "bird's eye" lesions on the berries and sunken black or greyish lesions on leaves and shoots. From these lesions, conidia are produced. This disease can be lethal to the plant, either through defoliation and removal of photosynthetic capacity, or through injury to the active regions of the vine. Grape anthracnose is particularly important to the wine industry, as it can decrease quality and quantity of berries produced as well as kill the vine outright, leading to large economic losses, in particular during the middle summer months.
Hosts and symptoms
E. ampelina affects two species of Rubus and three species of Vitis. Specifically, E. ampelina affects blackberries, raspberries, mountain grapes, fox or concord grapes, and the European wine grape. Anthracnose diseases can cause disease on a variety of plants, but the primary host for E. ampelina, is grape.
Anthracnose on grape presents itself as lesions on shoots, leaves, and berries. Lesions will first appear on young shoots, showing up as small circular reddish spots that will later become larger and create grey lesions which appear sunken. The lesions will eventually develop margins that are a dark reddish-brown to violet-black color. If left untreated, lesions on shoots will become larger and eventually kill the shoot. While these lesions may be very apparent and easy to identify, they can sometimes be confused for hail damage. Hail damage typically appears on only one side of the plants. Also, anthracnose lesions will have darker and more raised edge.
Anthracnose lesions on leaves and petioles look very similar to those on shoots. However, on leaves, the lesions will have dry grey or white centers that will eventually fall off, leaving a hole. This response by the plant is called a shot-hole. Should the lesions spread and the infection make it into the vascular system of the leaf, the anthracnose will prevent the proper development of the leaf and will lead to malformation or to the drying of the leaf.
Grape vines are susceptible to anthracnose before flowering all the way through fruit soften and coloration. Essentially, the berries are susceptible to the pathogen throughout the growing season. Anthracnose presents itself on the berries as small reddish circles, around a quarter inch in diameter, that will become sunken with a narrow dark brown to black border. Eventually, the center of the lesion will change color from violet to white or grey and become velvety. These lesions often look like a shooting target or bullseye. Should the disease spread to and affect the pulp of the berry, it will cause cracking, which opens the berry to secondary infections.
Disease cycle
Late in the season, the Grape Anthracnose fungus produces sclerotia, which are located primarily at the edge of the infected lesions on shoots. Unlike acervuli, sclerotia serves as the overwintering structures. Because the fungus over-winters in dormant and dead canes—one-year-old wood that starts to become lignified—disease control becomes very difficult.
Large numbers of conidia are disseminated from sclerotia in the spring when there are wet periods of 24 hours and temperature is above 36 °F (2 °C). The conidia infect the young leaves, shoots, and berries of the grape vine. Conidia will germinate, causing primary inoculum under the following circumstances: presence of free water in 12 hours and adequate temperature (36-90 °F (2-32 °C)). In fact, primary inoculum of Grape Anthracnose is possible even before bud break. The infection rate will escalate with increases in temperature. Development of disease symptom is also temperature-dependent: within 13 days at 36 °F, or within 4 days at 90 °F.
