A New Guide for Understanding Insect Vectors of Plant Pathogen Xylella fastidiosa

In many areas across the southern United States and California, one bacteria species complex is responsible for a long list of plant diseases: Pierce’s disease of grape, citrus variegated chlorosis, phony peach disease, plum leaf scald, alfalfa dwarf, almond leaf scorch, oleander leaf scorch, and leaf scorch of blueberry, pecan, and many shade trees. The bacterium, Xylella fastidiosa, attacks plant xylem, and its primary means of spreading is a variety of insects that specialize in drinking from that plant tissue.

In a new profile published last week in the open-access Journal of Integrated Pest Management, researchers in Oklahoma offer an in-depth guide to the biology and vectors of X. fastidiosa and the diseases it causes—with an eye toward the southern United States, where research on vectors and management practices has been less extensive than in California.

“There are unique features associated with each insect species that is capable of serving as a potential vector of X. fastidiosa. However, the first step to improving control practices for these species is to identify those insects feeding on a susceptible crop that can acquire the pathogen and transmit it to healthy plants,” says Eric J. Rebek, Ph.D., associate professor of entomology and plant pathology at Oklahoma State University and co-author of the research. The JIPM article is an adapted version of the literature review from the doctoral thesis of lead author Lisa Overall, who completed her Ph.D. at OSU in 2013 and is now an instructor of biology at Rogers State University.

“Dr. Overall conducted a survey of potential insect vectors occurring across the state, identified species harboring X. fastidiosa, and verified their ability to transmit the pathogen to susceptible plants through feeding assays. Armed with this information, we can now tell our growers what vector species to monitor, how to identify them, and how best to control them,” says Rebek.

As in California, the glassy-winged sharpshooter (Homalodisca vitripennis) is the most important vector of diseases caused by X. fastidiosa in the southern United States, but Overall’s research identifies a dozen other species that have been shown to vector the pathogen across the South, as well as some that reach the East Coast or even north into Canada. They include several species of sharpshooters in the family Cicadellidae, as well as three species of spittlebugs in the family Cercopidae.

Growers can employ a range of integrated pest management methods for glassy-winged sharpshooter, such as applications of imidacloprid and dinotefuran, screen barriers, and parasitoid wasps of the genus Gonatocerus. Researchers have also found that introducing a modified version of the glassy-winged sharpshooter’s gut bacteria through feeding can reduce its ability to transmit X. fastidiosa.

The JIPM profile also compiles various agricultural methods for reducing the spread of X. fastidiosa—a tricky pathogen that Overall and Rebek note is the only known insect-transmitted pathogen that can both reproduce in the insect’s foregut and spread to other plant hosts without first passing through the insect’s digestive tract. Rebek says the research will prove useful to growers in the southern United States.

“The Journal of Integrated Pest Management offers an ideal venue for publishing this type of work that typically ends up sitting on a shelf, unseen by most extension practitioners and stakeholders who can use the valuable information contained within a thesis,” he says.