The spotted lanternfly is a pest that is deadly to grape vines. A vineyard in Pennsylvania recently reported 90% crop loss due to the spotted lanternfly. The Pierce’s Disease/Glassy-winged Sharpshooter Board has received a few spotted lanternfly updates already. Entomologists believe that the spotted lanternfly will eventually spread to California likely in the form of egg masses on rail cars or other forms of goods movement. Egg masses may be hard to detect as they often look like accumulated mud. Below are links to critical information about the spotted lanternfly.
Xyella fastidiosa is a bacterium that lives in the water-conducting system (the xylem) of host plants and is spread from plant to plant by sap-feeding insects that feed on xylem fluid. Symptoms appear when significant blockage occurs within xylem vessels due to the growth of the bacteria. (This bacterium is also responsible for alfalfa dwarf disease and almond leaf scorch in California.) Insect vectors for Pierce's disease belong to the sharpshooter (Cicadellidae) and spittlebug (Cercopidae) families. The blue-green sharpshooter (Graphocephala atropunctata) is the most important vector in coastal areas. Helpful Links: UC Berkeley - Xylella Fastidiosa UC IPM - Pierce's Disease
Esca, Botryosphaeria dieback, Eutypa dieback, and Phomopsis dieback make up a complex of "trunk diseases" caused by different wood-infecting fungi. The foliar symptom of Esca is an interveinal "striping". The "stripes", which start out as dark red in red cultivars and yellow in white cultivars, dry and become necrotic. Foliar symptoms may occur at any time during the growing season, but are most prevalent during July and August.
Initial symptoms of powdery mildew appear on leaves as chlorotic spots on the upper leaf surface. Signs of the pathogen appear a short time later as white, webby mycelium on the lower leaf surface. As spores are produced, the infected areas take on a white, powdery or dusty appearance. On fruit and rachises the pathogen appears as white, powdery masses that may colonize the entire berry surface. Black to brown web scarring can be seen on mature fruit, which represents former colonies. Symptoms of powdery mildew infection include red blotchy areas on dormant canes.
The types of plant-parasitic nematodes that become established in a vineyard are determined by the nematodes present in the soil at planting, the nematodes in irrigation water, sanitation and cleanliness of nursery stock, susceptibility of the selected rootstock, the nematode host status of cover-crops and native vegetation, and the movement of nematodes with soil by vehicles. Of the many genera of plant parasitic nematodes detected in soils from California vineyards, dagger, ring, and root lesion nematodes are the most prevalent in north and central coast vineyards, and in the San Joaquin Valley.
Symptoms first become apparent in vineyards 5 to 7 or more years old, but the infections actually occur in younger vines. Perithecia, the overwintering structures that produce spores, are embedded in a stroma in diseased woody parts of vines. During winter rainfall, spores are released and wounds made by winter pruning provide infection sites. After a pruning wound is infected, the pathogen establishes a permanent, localized wood infection, which cannot be eradicated by fungicide applications.
the 10 grapevine leafroll-associated viruses (GLRaVs) are a group of viruses that cause similar symptoms in infected grapevines. They colonize and reproduce in the grapevine phloem tissue, which disrupts the flow of nutrients to shoots, leaves, and fruit pedicels. This disruption in vascular tissue stunts vines, reduces vigor, and impedes accumulation of sugars and other metabolites in the fruit. Infected vines often have fewer clusters, lower yield (up to 30-50%), and delayed fruit ripening.