The Crush - September 2019 - 1

Volume 46 Issue 9 September 2019


Status of Invasive Grape Pests in California
By Ted Rieger
The Crush presents an update on the status of three invasive
insect pest threats to California vineyards and one pest of major
concern outside of California that is being closely watched.

The glassy-winged sharpshooter (GWSS) (Homalodisca
vitripennis), a vector of Pierce's disease (PD), is a focus of the
California Department of Food and Agriculture (CDFA) Pierce's
Disease Control Program (PDCP) and the industry-funded PD/
GWSS Board. The five components of the PDCP are: contain the
spread, statewide survey and detection, rapid response, outreach
and research.
GWSS has mostly been kept in check in infested counties in
Southern California: San Diego, Riverside, San Bernardino, Los
Angeles, Orange, Ventura and Kern. GWSS infestations are in
parts of Santa Barbara, Imperial, Tulare, Fresno and Madera
counties. Since the PDCP began operation in 2000, 18 localized
GWSS infestations have been declared eradicated after rapid
response. In 2017, the last of six GWSS infestations in Santa Clara
County was declared eradicated.
The nursery shipment inspection program is a key component of
the PDCP to prevent the spread of GWSS north and statewide.
Trained inspectors monitor all nursery shipments (landscape
and other plants) from GWSS-infested areas at both origin and
destination counties. 2018 was the first year in the history of
the PD program that no viable GWSS life stages were found in
nursery shipments (a total of 34,400) at non-infested destination
locations. This year (Jan. 1 to July 31), of 24,903 nursery stock
shipments, just five viable GWSS egg masses were
found in shipments at destinations, resulting
in rejection of affected plant material.

No new GWSS infestations were found in California in 2018. Photo: Copyright ©
2014 Regents of the University of California. Used by permission. Jack Kelly Clark.

No new GWSS infestations were found in California in 2018,
and to date in 2019, the only new activity is a re-infestation in a
suburban area of Madera County near the San Joaquin River and
Fresno County line. Long-term infestations in Kern, Tulare and
Fresno counties are being managed through area-wide programs
and localized treatments to prevent GWSS spread.

While all species of mealybugs found in California can cause
damage from feeding, and can vector leafroll viruses, the vine
mealybug (VMB) (Planococcus ficus) is the most effective leafroll
vector and can potentially cause the most damage from feeding,
producing "honeydew" and increasing susceptibility to fungal
infection. The VMB produces more eggs and more generations
per season than other species and can be found on all vine parts,
including under vine bark and on roots when it overwinters and
is difficult to control by chemical applications. The VMB has

The Crush - September 2019

Table of Contents for the Digital Edition of The Crush - September 2019

The Crush - September 2019 - 1
The Crush - September 2019 - 2
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