AVF Proj. ID: 635
Year Funded: 2015
Category: ~ No Specific Category ~
Investigators: Kent Daane

Virginia Creeper Leafhopper Control

Organic grape growers in Mendocino and Lake County have been experiencing severe outbreaks of the Virginia creeper leafhopper (Erythroneura ziczac) since 2011. Feeding by E. ziczac causes leaf stippling and reduced photosynthesis which can impact crop yield and quality. High populations of E. ziczac adults in the fall can also be a nuisance, flying into the eyes, nose, and mouth of workers manually harvesting grapes. The primary natural enemies of E. ziczac are the small egg parasitoids Anagrus daanei and Anagrus tretiakovae (Hymenoptera: Mymaridae). A related pest, the Western grape leafhopper (Erythroneura elegantula) is also parasitized by A. daanei as well as Anagrus erythroneurae. Erythroneura ziczac and E. elegantula are commonly found together in North Coast vineyards. Anagrus daanei is the parasitoid species of most importance for E. ziczac control, whereas A. tretiakovae is rarely found in California.

Our approach to improving E. ziczac control involves a combination of short-and long-term strategies. Short-term work focuses on grower outreach/education to improve pest identification and timing of chemical controls while long-term strategies are focused on the identification, evaluation and introduction of Anagrus parasitoids to improve biological control.

In 2015 we held multiple outreach events (March 6 and November 20) and a field day (July 29) to review E. ziczac identification, management and provide updates on research progress and findings to date. There were also presentations made about the importance of leafhoppers in general in the transmission of grape “red blotch”. We also initiated a regional monitoring program to keep growers informed about the seasonal development of leafhopper populations in Mendocino County. Each week, at multiple vineyard sites, data were collected on adult leafhopper flights, egg deposition, nymph densities and parasitism rates. A summary of this data was then circulated to growers via a weekly email newsletter (http://ucanr.edu/sites/vclh/VCLH_Newsletter/). Finally, we established a project website (http://ucanr.edu/sites/vclh/) to serve as a repository of information on management of E. ziczac.

Our previous research has shown that although A. daanei is present in the North Coast, it does not attack E. ziczac. Surveys across northern California have identified another population or “strain” of A. daanei in the north San Joaquin Valley that will readily parasitize E. ziczac. As such, we proposed to collect, augment and release this novel strain of A. daanei into Mendocino and Lake County vineyards in order to establish biological control of E. ziczac. In 2015, more than 2,000 A. daanei were collected from Yolo County and released into a Mendocino County vineyard. Following these releases, parasitism of E. ziczac at the release site increased from 0% to 87-91%.

Also of importance is to note that in June 2015 our research group received a large grant

from the California Department of Pesticide Regulation “Pest Management Alliance Program”

that will provide funding for this research program through March 2018. These funds will allow for the continued importation and release of A. daanei into Mendocino/Lake County vineyards, as well as support the on-going outreach and education efforts with growers, including the regional monitoring of leafhopper populations.

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