Grape growers field day focuses on new vine menace

The dreaded vine mealybug was the hot topic at the Sonoma County
Grape Growers Association’s Integrated Pest Management Field Day on
August 6 at SRJC’s Shone Farm on Eastside Road.
“I’m afraid that if you have it, your control options are the
very chemicals we’re trying to move away from,” said association
Executive Director Nick Frey of the mealybug, a new exotic
pest.
Jim Raisner, an Agricultural Biologist Standards Specialist with
the Sonoma County Agricultural Commissioner’s office, said the
mealybug (Planococcus ficus), threatens vine health and grape
salability.
The mealybug, so called for the mealy wax coating that covers
its body, has infested vineyards in the Mediterranean region during
the 20th century and was discovered in California in 1994,
according to U.C. Davis.
The small (quarter-inch long), pink pest spends its whole life
cycle — from egg to adult — on the vine, feeding on plant juices
and excreting a sweet substance that attracts ants and exacerbates
mold problems.
“This year we trapped at 75 locations in the county and found
four infestations,” explained Raisner. Two of those were close
together in the Carneros appellation. Others were found in the
Russian River and Alexander valleys.
Raisner said he thinks the mealybug was introduced from young
bugs or eggs in infected nursery stock, so the Ag Commissioner’s
office is concentrating on investigating vineyards that have put in
new plants since 1998.
“If you’ve put in new vines in the past five years, come on into
the office,” he said. “We have traps. If you put the traps out then
bring them back in, we’ll read them for you.”
Raisner said it is vitally important to keep infestations from
spreading. Since the insect is primarily spread by human activity
the infestations can be contained if the right procedures are
followed.
“Several counties are looking at passing ordinances to control
the movement of grapes and planting material” because of the
mealybug, he said. “If that happens, we may have to certify your
grapes if they’re going to that county, or require treatment … this
might affect you in the next year or two.”
Keith Abeles of Community Alliance with Family Farmers spoke
about his two-year project to encourage local growers to plant
hedgerows of native plants to encourage populations of beneficial
insects.
“A hedgerow can be bushes, trees or shorter plants like yarrow
or buckwheat,” he explained. “They attract and host beneficial
insects, … control soil erosion, (and) are buffers to dust and
spray. Once mature, they shade out weeds, act as windbreaks, act as
a privacy shield, are good for habitat restoration and
connectivity, and can be beautiful. … A hedgerow is an opportunity
to build a more diverse system, to create a more balanced, healthy
environment for your vines.”
Abeles encouraged growers to use native plants in hedgerows
because they support native insect and animal species and use less
water.
Abeles said grants and other help for native plantings are
available through the Natural Resources Conservation Service’s
Environmental Quality Incentives Program, by calling 794-1242, ext.
3.
For more on hedgerows, references for nurseries and professional
contractors, or to participate in CAFF’s hedgerow program, contact
Abeles at 823-6788.
Shone Farm manager Leonard Diggs and Jeanette Wilhelmsen spoke
on their research into targeted irrigation.
“We needed to know baseline information,” explained Diggs about
a two-acre chardonnay block. “Last year we dug 24 soil pits in the
field to find out soil characteristics and water-holding
capacity.”
Diggs said they want to learn to keep the effective root zone of
the vines — the roots that will absorb water the best — at the
optimal moisture level for each time of the growing season.
“Between now and verison (when the grapes begin to turn color)
is the time to start pushing that edge — to hold the water back,
go to the limit” of minimal irrigation, he said. Giving the vines
less water now will result in lower yields of higher quality grapes
with more concentrated flavor — a good strategy if you have a
buyer and want to keep your volume low, he said.
IPM field specialist Laura Breyer spoke about the Association’s
vineyard monitoring at several Sonoma County vineyards.
The pinot has had variable levels of mites with compensating
levels of mite predators, she said. Mites and leafhoppers are
causing light damage to the merlot. The zinfandel and cabernet are
having a problem with Pacific mites that is being addressed to some
effect with Stylet oil (a mineral oil) and other sprays.
For more on upcoming Sonoma County Grape Growers Association
events, visit www.scgga.org or call 829-3963.