DOI: 10.5061/dryad.59zw3r2h9
title: Trap counts and natural infectivity of blue-green sharphooter

description: Effective disease management hinges on an accurate understanding of the
 ecological and epidemiological underpinnings of the pathosystem. New
 epidemics may prompt consideration of whether knowledge gaps or changes to
 the pathosystem warrant revision of management strategies. Pierce’s
 disease of grapevines (PD) is highly episodic in coastal Northern
 California vineyards, with modest incidence in most years punctuated by
 occasionally severe epidemics. To better understand what was driving a
 developing epidemic in the region, we revaluated what is known about the
 ecology and epidemiological role of the dominant vector, the blue-green
 sharpshooter Graphocephala atropunctata. We monitored vector
 spatiotemporal dynamics at 32 vineyards over three years, surveyed plant
 community composition in the adjacent habitat to understand its link to
 vector recruitment, and quantified patterns of natural infectivity for the
 pathogen Xylella fastidiosa. Overall, the results were consistent with
 past studies of G. atropunctata ecology. For example, the scale of
 dispersal from source habitat and seasonal patterns in activity were
 generally similar to those documented in prior studies. The results also
 confirmed the influence of adjacent plant community composition on G.
 atropunctata activity in vineyards, and the role of riparian habitat and
 select plant taxa as vector sources. Nonetheless, further consideration of
 the epidemiological significance of certain features of the pathosystem
 may be warranted, especially those related to seasonality in X. fastidiosa
 natural infectivity. A marked increase in infectious G. atropunctata late
 in the season likely reflects pathogen acquisition from infected
 grapevines, which may have implications for disease management strategies.
description: <strong><em>Graphocephala
 atropunctata</em></strong><strong>
 monitoring:</strong>
 <strong> </strong>Monitoring for the dominant vector
 in the region, <em>G. atropunctata,</em> was conducted at 32
 commercial vineyards in coastal Northern California, spread throughout the
 central viticultural regions in Napa and Sonoma counties. The vineyard
 sites were selected in part to capture variation in acreage, surrounding
 landscape context, vector abundance, and disease pressure. At each
 vineyard, we deployed between 6 and 15 yellow panel traps (10.2 x 17.8 cm
 double-sided yellow panel traps; Seabright Laboratories, Emeryville, CA),
 depending on vineyard size and shape, for a total of more than 375 unique
 traps. Traps were distributed in two to three transects per site running
 from the edge of the vineyard into the interior. At each site we also
 placed one to three traps on the periphery of the vineyard nearby the
 closest putative vector source habitat (“vegplot" traps). Each trap
 was checked twice per month over the growing season and once a month in
 the dormant season
 <strong><em>Graphocephala
 atropunctata</em></strong><strong> natural
 infectivity:</strong>
 <strong> </strong>To better understand patterns of
 natural infectivity in vector populations, we screened all <em>G.
 atropunctata </em>collected on traps for the presence of
 <em>X. fastidiosa</em>. After collecting sticky traps during
 the monitoring program described earlier, sharpshooters were individually
 removed from traps, cleaned, DNA was extracted and subjected to real-time
 PCR to determine the fraction positive for<em> X.
 fastidiosa</em>. Insects were removed from sticky
 traps and agitated in a xylene-like solution, Citrisolv (Decon
 Laboratories Inc., King of Prussia, PA), for 30 seconds to remove adhesive
 residue. They were then subjected to three consecutive washes in 100%
 ethanol for a minute each to minimize residue carryover. Next, we used
 sterilized forceps to isolate individual sharpshooter heads. DNA was then
 extracted from insect heads using Qiagen’s DNeasy 96 Blood and Tissue Kits
 (Qiagen Inc., Santa Clarita, CA), eluted in 100uL buffer AE. Real-time PCR
 was run using Promega’s GoTaq® qPCR Master Mix reagents (Promega
 Corporation, Madison, WI) on an Applied Biosystems™ 7500 Real-Time PCR
 thermocycler under the following conditions: 95°C for 15min, then 40
 cycles of 95°C for 10 secs, 60°C for 15 secs, and 72°C for 30 secs. The
 primers utilized were PD0059 at 0.30uM final concentration (PD0059_For
 GCTTCGGCCACTGACATATT, PD0059_Rev GCAAGGTTCACAAGCACGAT; Sicard et al.
 2019). Positives samples were determined by the presence of a Cq value and
 a Tm between 82.24-84°C.
description: # BGSS counts
 [https://doi.org/10.5061/dryad.59zw3r2h9](https://doi.org/10.5061/dryad.59zw3r2h9) Number of *Graphocephala atropuncata* (“BGSS”) adults caught on more 375 individual yellow sticky traps spread among 32 vineyard sites in Napa and Sonoma counties, California, from March 2016 through November 2018. “site” denotes the unique identifier of the 32 vineyard sites “site.type” denotes vineyard sites that were located adjacent to one of three categories of surrounding vegetation: riparian habitat, oak woodland or chapparal, or grassland or other habitat “trap” denotes the unique identifier for the more than 375 separate yellow sticky traps, whose locations did not move appreciably over the study “trap.type” denotes whether the trap was located within the vineyard block (“vineyard”) or was located on the edge of adjacent vegetation (“vegplot”) to the vineyard block “distance” denotes the approximate distance in meters from the trap to the edge of vegetation adjacent to the vineyard “date” denotes the date the trap was collected and insect vectors were counted # BGSS natural infectivity Infection “status” of individual *Graphocephala atropuncata* adults for *Xylella fastidiosa* (1 = positive, 0 = negative) caught on more 375 individual yellow sticky traps spread among 32 vineyard sites in Napa and Sonoma counties, California, from March 2016 through November 2018 “site” denotes the unique identifier of the 32 vineyard sites “site.type” denotes vineyard sites that were located adjacent to one of three categories of surrounding vegetation: riparian habitat, oak woodland or chapparal, or grassland or other habitat “trap” denotes the unique identifier for the more than 375 separate yellow sticky traps, whose locations did not move appreciably over the study “trap.type” denotes whether the trap was located within the vineyard block (“vineyard”) or was located on the edge of adjacent vegetation (“vegplot”) to the vineyard block “distance” denotes the approximate distance in meters from the trap to the edge of vegetation adjacent to the vineyard “month” denotes the month of the year the trap and insects were collected, where 1 = January and 12 = December “year” denotes the year of the corresponding month that the trap and insects were collected