The Crush - May 2020 - 1

Volume 47 Issue 5 May 2020


Ant Management in Vineyards

By Ted Rieger
Managing and controlling ants in vineyards is important for
managing mealybugs that pose a significant threat to grapevines
as leafroll virus vectors, in addition to their potential for
damaging the grape crop. Some ant species protect mealybugs
in order to feed on sugary "honeydew" produced by mealybug
feeding activity in grapevines. As a result, ants disrupt integrated
pest management (IPM) by interfering with natural predators
and parasites that assist with mealybug control. In addition, ants
can help spread mealybugs within vineyards and can maintain
below-ground colonies of mealybugs near vine trunks and on
vine roots.
It is important to identify the ant species present in a vineyard
to determine its potential as an economic threat, and to target
control methods using insecticidal ant baits based on the species'
preferred diet.
Dr. Kris Tollerup, University of California Cooperative
Extension (UCCE) IPM advisor, has studied ant populations
and management in California vineyards and orchards. He
is working with the Lodi Winegrape Commission (LWC) to
monitor ant populations and conduct ant control field trials in
Lodi vineyards. "We need to develop better ant monitoring and
control for winegrapes," Tollerup said. "We have ant baits, but
they are not effective for all ant species."
Tollerup said about 300 ant species are known in California, of
which 30 are introduced or non-native. Based on his experience,
he said, "Collecting, identifying and monitoring ants in vineyards
is important, as we're seeing more evidence that there
are more species out there that are tending
mealybugs than just the Argentine ant, which
has been the main focus for some time."

The pavement ant is one of five ant species that commonly occur in San Joaquin
Valley vineyards. Photo: Roland Schultz, Ant Web

Tollerup has identified five ant species that commonly occur
in San Joaquin Valley vineyards: the native gray or field ant
(Formica aerata), pavement ant (Tetramorium immigrans), two
fire ant species - southern fire ant (Solenopsis xyloni) and thief
ant (Solenopsis molesta) - and the highly invasive Argentine ant
(Linepithema humile). In coastal vineyards, the Argentine ant is the
main species of concern.
Other ant species found in vineyards include the pyramid ant
(Dorymyrmex bicolor), honeypot ants (Myrmecocystus species),
Myrmicinae ant species, and additional Formica species.
The harvester ant (Pogonmyrex californicus) has been seen in
vineyards. Tollerup said it doesn't feed on honeydew, but it can
sting, so it's a potential nuisance for workers. Other ants more
commonly found in residential settings may be encountered in
vineyards. The carpenter ant (Camponotus species) is commonly
found in wood structures, but it will feed on honeydew from
plants produced by aphids, whiteflies and scale.
Tollerup is helping conduct an areawide survey of ant species in
Lodi, with growers obtaining sample vials from the LWC to place
in vineyards to collect ants and return them for identification.
Tollerup also plans to work with UCCE IPM advisor Cindy


The Crush - May 2020

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