BY Laura Breyer
Growers in Napa and
Sonoma Counties are approaching the fifth year of living with vine
mealybugs (Planococcus ficus [VMB]) and are developing
management programs based on University of California (UC) recommendations,
modified by their own inventiveness.
Initial infestations are usually found in the late summer, and are
treated very aggressively with foliar applications of Lannate (methomyl)
or other broad spectrum insecticides to reduce the mealybug population
and to keep them from spreading. (Lannate has a 21-day REI when
applied after August 15 due to California Worker Protection Standards,
not seven days as on the label.)
Bark stripping, though laborious, can also be part of this aggressive
strategy. It allows better contact of the spray material on VMB
residing under the bark on trunks and cordons.
Some growers have even tried removing infested vines. In the first
years after VMB appeared in California, these intensive efforts
were aimed at eradication. However, even though populations may
be reduced to below detectable levels for a year or two, they eventually
come back to unacceptable levels. It can be very difficult to ascertain
if a vine has mealybugs or not, due to the very small size of the
VMB was not the only mealybug causing trouble in 2005. Grape mealybug
(Pseudococcus maritimus [GMB]), and the less common obscure
mealybug (P. viburni [OMB]) populations were unusually high,
obligating many growers to treat mid- to late-season for control
of mealybugs already fairly well hidden in clusters. The successes
here may translate to VMB management.
After mealybugs move into the clusters, foliar-applied materials
often have very little benefit for mealybug control, most likely
due to the difficulty of getting coverage in the clusters when mealybugs
are still small enough to control easily.
Dana Grande, viticulturist with Jordan Vineyard & Winery (Healdsburg,
CA), used 8 oz of JMS Stylet-oil and 12 oz per acre of Applaud (buprofezin)
in 100 gallons [water] per acre, directed at grape mealybug crawlers
in grape clusters in early August. Three weeks after treating, Grande
reported, Unbelievable control
I couldnt find
one mealybug in the clusters.
Don Mitchell with Purity Products (Healdsburg, CA) achieved excellent
control of grape mealybug in Carneros Chardonnay clusters in late
summer with dimethoate at 2 qt in 400 gallons [water] with an organosilicon
spreader. Dimethoate is generally on the wane as a highly-regarded
pest management tool due to its association with disrupting mite
populations and potential human health risks being an organophosphate,
but as an inexpensive rescue tool in mealybug management, it can
play a role if utilized correctly.
For vineyards with heavy clay soils where Admire (imidacloprid)
is ineffective against mealybugs, Valent has a new Venom
neonicotinoid product (dinotefuron) that acts systemically like
Admire but may perform better in heavy soils. (The cautious grower
may want to test this new material on a small acreage in a mealybug-infested
site before large application.)
The application method differs significantly from Admire; company
representatives recommend putting Venom in towards the end of a
chemigation cycle, since it moves readily and will travel past the
root zone if put in at the beginning of an application, as is done
with Admire. Contact your PCA or Valent representative for more
One important difference in the overall chemical management of VMB
compared to GMB or OMB is that a post-harvest foliar insecticide
application is recommended to reduce VMB populations from spreading
on wind-blown leaves and returning to the trunk and cordons to over-winter.
Treating for GMB or OMB after harvest is not
recommended since GMB or OMB have generally moved out of the canopy
by that time. See PWV (Jan/Feb 2006) for a detailed article
on the biology and identification of each mealybug species (Which
Mealybug is it, and Why Should You Care, L.Varela, et al).
Not only were mealybug populations elevated in 2005 in the Napa
and Sonoma region, but the population of ants tending mealybugs
in vines was also noticeably higher. In many older vineyards that
I monitor, GMB (and less commonly OMB) is an innocuous part of the
bioscape and rarely an economic pest. When monitoring mealybug nymph
populations in the future, I will be more likely to trust noticeable
increases in ant activity as an additional indicator of unusually
elevated mealybug populations.
If there are many active ants in the vines again, I will target
ants on the ground with a strip-spray Lorsban (chlorpyrifos) treatment.
This is because GMB and OMB are generally under fairly good biological
control in the grape canopy when the predators and parasites are
undisturbed by ants or pesticides.
It is important to note that Lorsban can only be used for ant control
or as a dormant vine spray for mealybug control, but not for both
pests in one season. Although VMB is currently not as well-managed
with bio-control in California, reducing the ant population will
likely help increase predation of the mealybug population; one component
in an overall management strategy.
Ant bait stations are being developed and they will be welcome additions
for all mealybug integrated pest management (IPM) programs. Kent
Daane and other UC researchers are working on the main culprit Argentine
ant (Linepithema humile), studying its biology and
behavior in the field so we will know when, where, and how to best
deploy the stations. Bayer and other companies are working on registering
effective materials. Regulatory agencies are working on approving
bait stations and chemical materials for agricultural use. There
may be a commercial product available in 2007.
It is likely that there will be an organically-approved boric acid-based
bait in addition to conventional bait. Daane and others are also
working to establish parasites that will help reduce VMB populations
to similar levels of resident mealybugs. Mating disruption with
pheromone is also under investigation.
Although more foliar insecticides, insect growth regulators (IGR),
and systemic chemigation materials will be used in VMB-infested
vineyards than in pre-VMB days, hopefully we will also become more
aware of the resident predators and use them to our advantage by
developing IPM programs for VMB that effectively utilize chemical
tools while conserving the beneficials.
For example, a dedicated IPM or organic grower who has mealybug
destroyer beetles (Cryptolaemus sp.) working effectively
on mealybug may not want to use the soft insecticide Applaud in
the North Coast since it is an IGR and therefore prevents immature
insects, including the mealybug destroyer, from developing into
adults. The recommended timing of Applaud for the late spring or
early summer in the North Coast coincides with the juvenile stage
of the beetle, and according to UC IPM Guidelines, may compromise
Devin Carroll, past-president of the Association of Applied IPM
Ecologists (AAIE), has posted a list of grape mealybug natural enemies
on the AAIE website, www.aaie.net. The most important are parasitic
wasps in the family Encyrtidae, and the predaceous gall midge, Dicrodiplosis
californica. Also on the list are mealybug destroyer beetles,
lacewings (Chrysopidae), some spiders, earwigs (Forficulidae), and
carpet beetles (Dermestidae). Ground beetles (Carabidae) and a minute
pirate bug, Dufouriellus ater, are also associated
with mealybug colonies but have not been observed attacking them.
Many people find it remarkable that earwigs are omnivorous (feed
on more than plant material), but they are well-known to grapegrowers
with hand lenses as predators and have been observed eating mealybugs.
Predaceous maggots of the gall midge, and carpet beetles are also
among the amazing-but-true beneficials working quietly in vineyards.
Another aspect of VMB management that I have not seen emphasized
very widely is deterring birds. We are meticulous about making sure
crews and equipment are clean before leaving a VMB-infested vineyard,
but allow birds free access to feed in the infested clusters where
they can become contaminated with VMB, and then move at will to
neighboring blocks and vineyards, spreading the pest to new sites.
Riparian areas, large trees and roosting locations such as power
lines, complicate the control of birds moving in and out of vineyards
all season long, always with the potential to spread mealybugs.
Such areas are good spots to monitor for initial infestations. For
growers with an infestation or near an infestation, employing bird
deterrents just before veraison would seem to be a prudent strategy.
The Vine Mealybug Workgroup in Napa and Sonoma Counties, along with
implementing a coordinated trapping program, is working on a sniffer-dog
program that will allow better detection of VMB in the field by
utilizing the outstanding olfactory system of dogs rigorously trained
with similar methods to those used by search and rescue or security-detection
We have been living with grape mealybug, and obscure mealybug on
the North Coast of California for years. Natural predators and occasional
intervention with pesticides or ant controls have limited their
damage with regard to grape quality or yield.
However, vine mealybug poses a much greater threat, and while treatment
practices will continue to evolve, we are developing the tools and
knowledge to find, reduce damage, and limit the spread of this new