"I figured if the insects didn't work,
we could always fall back to the insecticide
program," Rosenbrand explains.
The insect-release program began in
2006. "We released everything that
would eat a mealybug," he recalls.
They released predators, which consume
all VMB stages from egg to
adults, and parasitoids, which lay eggs
inside the VMB and eat it from the
"The two strategies are complementary,
not contradictory," Rosenbrand
says. "The difference is that some of
the predators tend to work best in
high-density populations, while parasitoids
can work well at both high and
low density populations, and they are
not as likely to disperse."
Although the insecticide sprays
(Lorsban, Lannate,Dimethoate, Provado,
and Applaud) were not successful in
eradicating the mealybugs, they did
serve a useful purpose. First, they kept
the VMB population below damaging
levels. Second, although they weren't
the target at the time, Argentine ants,
were also victims of some of the insecticides.
A large Cryptolaemus larva (the mealybug
destroyer) feeding on a mealybug "ovisac."
A large larva of the mealybug destroyer
(Cryptolaemus) next to a small mealybug.
"The sprays killed everything except
the mealybugs beneath the bark. But it
did kill the ants," Rosenbrand recalls.
"That meant we could start with a
"The Argentine ants may directly
kill some beneficials," explains Cooper,
"but mainly the ants protect the mealybugs
by disrupting the behavior of the
beneficials (parasites are unable to lay
eggs and predators are unable to consume
The UC Berkeley team began releasing
insects one month after bud break
in 2006 — 18,000 Coccidoxenoides perminutus
(a small, black parasitic wasp),
on April 19. One day later 30,000 ladybugs
were released, 50,000 green lacewings,
and 2,000 minute pirate bugs.
On April 25, 5,000 Cryptolaemus montrouzieri
(beetles appropriately named
the "mealybug destroyer") were
released, and one week later, 80,000
more ladybugs. On May 17, the parasite
Anagyrus pseudococci (a brown parasitic
wasp with white-tipped antennae)
was released, with 50 females and
"In the beginning, my strategy was
eradication," recalls Rosenbrand. "We
released everything we could obtain.
Now things have changed somewhat
to a more refined approach using
insects that have proved their success."
During the months that followed,
various quantities of those insects were
released. All predators were purchased
by Rosenbrand through a commercial
Closeup of vine mealybug female.
parasitoids were part of
a joint UC and California Department
of Food and Agriculture bio-control
"The C. perminutus were imported
from South Africa and the A. pseudococci
were brought in from northern
Italy, both were collected on VMB and
may perform better than the native
parasites," Daane explains.
By the end of the season, Rosenbrand
and the UC Berkeley team had
released 1,765 Anagyrus, 94,650 Coccidoxenoides,
35,000 Cryptolaemus, 670,000
ladybugs, 10,000 minute pirate bugs,
and 700 cards each containing 500
green lacewing eggs for a total of
The scientists sampled mealybug
populations between April and
October, and monitored parasitism
rates and economic damage to grape
clusters before harvest. From these
mealybug samples, both A. pseudococci
and C. perminutus were recovered, thus
confirming their ability to reproduce
under field conditions.
Pheromone cards play big role
In addition, 2,500 pheromone card-
dispensers were placed in June; they
lasted through the season. "Pheromone
cards are a big part of the program,"
Rosenbrand explains. "The cards contain
the synthetic version of the sexual
attractant of the female VMB that
attracts the male."
"Each card slowly releases the
equivalent scent of 10,000 female
mealybugs," Cooper adds.
According to Daane, the actual
mechanics behind the "mating disruption"
are not yet understood because
the unmated female can still produce
eggs. The researchers believe that
application of the synthetic sex pheromone
may reduce the number of
female eggs produced, and it might
help stimulate the parasites to look for
VMB in the vineyard.
"I feel there is a favorable impact
from the cards," Cooper reports,
"although, to date, we have not been
able to isolate that impact in our experimental
trials." The downside to pheromone
cards is that they can disrupt the
work of vine mealybug scent detection
dogs, making it harder for them to find
their live target."