Vineyard Pests & Diseases

Below you will find information on pests and diseases that are damaging to vineyards and winegrapes.

Spotted Lanternfly

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. 

  • Slide show created by Dr. Kyle Beucke, Primary State Entomologist, California Department of Food and Agriculture.
  • Recommended Best Management Practices Preventing Spread of Spotted Lanternfly for the Wine and Vineyard Industry.  Prepared by Penn State University.

Pierce's Disease

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

Measles and Young Vine Decline

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.

Measles (Black Measles and Spanish Measles)


Prior to fruit ripening, early-season shoot blight may occur following prolonged warm moist conditions caused by frequent spring rains. Patches of soft brown tissue develop resulting in the death of the infected plant part. Infections often occur in leaf axils causing shoots to wilt or break off. At veraison, individually infected berries in a cluster turn brown on white cultivars or reddish in red and black cultivars. If temperatures are moderate, moisture is high, and wind speed is low, epidermal cracks will form in which fungal growth produces mycelium and spores, resulting in the char­acteristic gray, velvety appearance of infected berries.

Botrytis Cinerea of Grapevines
UC IPM: Botrytis Bunch Rot

Powdery Mildew

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.

Control of Powdery Mildew Using the UC Davis Powdery Mildew Risk Index
Grape -- Powdery Mildew

Epidemiology and Management of Grape Powdery Mildew
UC IPM: Powdery Mildew

Vine Mealybug

Vine mealybugs are small (adult females are about 1/8 inch in length), soft, oval, flat, distinctly segmented, and covered with a white, mealy wax that extends into spines (filaments along the body margin and the posterior end). The vine mealybug has a pinkish body that is visible through the powdery wax, and it is slightly smaller than the Pseudococcus mealybugs. The waxy filaments that protrude from the body of the vine mealybug are shorter than those on the Pseudococcus mealybugs, and the vine mealybug does not possess long tail filaments. The adult male is smaller than the female, has wings, and flies short distances to mate. There are three to seven generations a year.

UC IPM: Vine Mealybug

Fanleaf Virus

Plant-parasitic nematodes are microscopic, unsegmented roundworms that feed on plant roots by puncturing cell walls and withdrawing cell contents by means of a protrusible hypodermic structure called a stylet. They live within root tissues and in the water films that surround soil particles and roots.

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.

Nematodes (Vector of Fanleaf Virus)


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.

Grape Eutypa Dieback

Leafroll Virus

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.


Grape Phylloxera