Most folks have heard of the glassy-winged sharpshooter and how it spreads the pathogen that causes debilitating Pierce’s disease in grapevines. The pathogen also causes disease in other plants such as olive and citrus. In grape, Pierce’s disease has been a problem for 100 years. Each year, California spends approximately $104 million via yield loss and on the management of the disease.
Fewer might know that other bugs can also vector the pathogen that causes Pierce’s disease. The spittlebug, Aphrophora nr. permutata, is also a vector. It was not considered an important vector because they were rarely found in vineyards. However, recent observations of diseased vines far from riparian areas—with the more common vectors (i.e., sharpshooters) the typical pattern of infection is diseased vines near riparian areas—suggests spittlebugs could play a role in outbreaks. The role of this spittlebug in Pierce’s disease outbreaks in North Coast vineyards is poorly understood.
UC IPM Area Advisor Cindy Kron joined the project in the third year to fill the roles left when Rhonda Smith and Lucia Varela retired. Funded with a California Department of Food and Agriculture Pierce’s Disease and Glassy-winged Sharpshooter grant, Kron worked to wrap up Sonoma County’s part in the project. Kron and colleagues documented the ecology of A. nr. permutata in North Coast vineyards: what habitat surrounding the vineyard supports this spittlebug and reconfirmation that this spittlebug transmits the pathogen that causes Pierce’s disease.
Research confirmed that the spittlebug associated more with certain plants than others and were found more often in woodland and riparian habitats than grassland habitat or agricultural areas. Preliminary transmission experiment results were a 5 to 7.7% transmission rate of the pathogen that causes Pierce’s disease by the A. nr. permutata spittlebug. Low transmission and low numbers in vineyards suggest that the role of this spittlebug in Pierce’s disease outbreaks is minor.
Improved understanding of the relationship between a disease-causing pathogen and its insect vector can lead to knowing whether an insect is a pest and should be managed or not. Kron and colleagues’s research looked at the biology of a spittlebug vector to determine if management strategies were needed to prevent Pierce’s disease outbreaks in North Coast grapevines. Understanding the biology, ecology, and vector capacity of insects is an essential first step to knowing if an insect is a vector and developing an IPM program if one is needed. In this case, the role of the spittlebug in Pierce’s disease outbreaks is minor, thus saving the cost of pest management and preventing unnecessary pesticide applications. IPM programs focus on the long-term prevention of pests and their damage through a combination of management practices that minimize the risk of pests or pest management practices to humans, other organisms, and the environment.
Kron’s article: Assessment of nymphal ecology and adult Xylella fastidiosa transmission biology of Aphrophora nr. permutata (Hemiptera: Aphrophoridae) in California Vineyards. Environmental Entomology, 50(6), 2021, 1446–1454. https://doi.org/10.1093/ee/nvab081
