Central Coast Meeting:
Updates Growers/PCAs on Pests and
By Patrick Cavanaugh,
Editor, and Laurie Greene, Associate Editor
|Crowd Listens in the Bonipak Conference Room,|
At the UC Annual Santa Maria
Vegetable Meeting today in the Bonipak Conference Room, about 75 growers, PCAs
and others came to hear the latest in vegetable disease and insect management,
as well as food safety and proper pesticide use.
UC Cooperative Extension plant pathology Farm Advisor in Monterey County, spoke
about diseases of coastal vegetable crops.
Koike elaborated on new races
of downy mildew. “About every 18 months to two years, we see a new race. Currently
we are on race 14, and we still have races 10 through 13 affecting crops,” he
said, adding, “2013 has been fairly quiet for downy mildew.”
“With the increased variety
of crops, we see an increased variety of root rot diseases such as Pythium, Phytophthora, Fusarium oxysporum,
and Rhizoctonia. For instance, with
the higher popularity of spinach, we see more root rot issues.” He noted that
growers are seeing a buildup of Pythium in their fields, which affects the
plant early in the season and causes the whole root to die. While Phytophthora
is still quite rare, Fusarium is less rare and causes the root tips to turn
back. “Rhizoctonia is the third major disease affecting older plants, again,
turning the root tips necrotic black.”
Koike then spoke about
several viruses that affect Central Coast crops. He said that impatiens
necrotic spot virus (INSV) has been found worldwide; in Salinas, INSV has been
discovered on lettuce. “It’s very
important in lettuce but it can also be found in basil, celery, endive, fava
bean, peppers, radicchio spinach, and tomato plants. We have lettuce fields in
Salinas with 60% INSV, and growers walk away from these fields,” he said.
“INSV and many other viruses
are vectored by thrips, which are difficult to manage all season long,” noted
Other major viruses include
lettuce necrotic stunt virus (LNSV) and tomato bushy stunt virus (TSWV).
“We are seeing yet another
virus, tomato spotted wilt virus, starting to show up on artichokes. Artichokes
are a known host, but it is rare to see the virus affect the crop by causing
necrotic streaking in the plant’s stems,” said Koike. “We are concerned that it
could be a new strain.”
Koike explained that some Wilt
diseases found elsewhere are now moving to the Salinas Valley. For instance, Verticillium Wilt and Fusarium Wilt damage on lettuce have not
been detected in this area yet, but need to be watched.
“Before the restrictions on
methyl bromide, we did not see these wilt diseases when lettuce and
strawberries were rotated around each other,” Koike commented.
“As growers phase out methyl
bromide, they have been using bed fumigants of straight Chloropicrin or Chloropicrin plus Telone,” Koike continued. “These have not been as effective as
methyl bromide, so when fields are reworked for the next rotation crop, more
Verticillium is present, causing yield decline.”
Koike then turned to powdery
mildew in Salinas, which is becoming more important in Salinas, especially on
lettuce, which had normally not been a problem.
“Powdery mildew on celery is
increasing in that now we can see significant symptoms,” Koike remarked. “In
fact, if growers can see the symptoms when they drive by the field, then you
know there is a problem,” he said.
In other topics at the annual
meeting, Heather Scheck spoke about
bacteria wilt and brown rot in potatoes caused by Ralstonia Solanacearum.
“This wilt is very difficult
to control, and it could eventually be a problem in North America due to a new
race known as Race 3, Biovar 2,” she said. “At risk are both tomatoes and
Scheck said that the
ornamental geraniums are a big host plant of Race 3, Biovar 2. “Geraniums are
imported to the U.S. from the Netherlands, Kenya and Guatemala, and a big outbreak
for Race 3, Biovar in 2004 forced crop destruction in these countries to
prevent exportation of the bacterial wilt,” she said.
“There is no chemical
treatment for the problem in geraniums,” Scheck said.
Also speaking was Lisa Blecker, Pesticide Safety
Education Coordinator with UC Agriculture and Natural Resources (UCANR), UC
She focused on crop
protection product labels and the importance of following the label especially
specific use restrictions. Pesticide tolerances are legal residues, based on
the EPA allowances.
“Most crops have pesticide
residues, but they are far less than what causes harm to consumers. Tolerances
are critical for human health,” she noted.
Tolerance is based on:
- Good human health, with no observable harm
- Assumption of maximum use of product
- Assumption of maximum applications per year
“If growers or those who
apply products follow label directions, you will not go over tolerance,” she
Strawberry and Vegetable Crops Advisor/Affiliated IPM Advisor for San Luis
Obispo County spoke about managing thrips on lettuce, aphids on broccoli and the
new invasive pest, Bagrada bug, on cole crops.
“Western Flower Thrip is a
sucking insect that vectors viruses,” he said, “and I did experiments on
lettuce using many different products.”
Research has found that
thrips can be significantly lowered with chemical treatment versus untreated
control. “Softer materials such as Tolfenpyrad alone or with methomyl provides
good control,” he said. “Also, some microbial products have potential for thrip
Surendra then spoke about the
cabbage and green peach aphid, a particular problem for broccoli, especially at
post harvest. He tested several control products in a trial.
He noted Asana did very well
on cabbage aphid but not as good on green peach aphid. “However, tests showed
that Dow AgroScience’s Sulfoxaflor provided good control for both aphids
“We also treated aphids with
a friendly fungus called Beuveria
Bassiana, that is showing promise,” Dara said.
Dara moved on to the Bagrada
Bug, which was discovered in Los Angeles County in 2008 and is now prevalent in
all southern California counties, plus Monterey County. “This pest has a wide
host range of vegetables and ornamentals,” noted Dara. “And there is a low
threshold for damage because one adult per 10 foot row of seedlings or transplants
will cause a stand loss.”
Dara said it’s important to
identify the adult Bagrada Bug and closely monitor it during the early 5-6 leaf
stage of plants.
“There are many different registered
control products that are effective for the pest,” Dara said. He is also
working on non-chemical controls such as Fungi, NoFly and essential oils, all
of which show promise.
According to Dara, cultural
- consider removing weed hosts
- ensure transplants from nursery materials are bug free
- cultivate to destroy bugs and eggs in soil
- shred and disc crop immediately after harvest
- rotate to non-host crop when possible
For a video on Bagrada Bug,
More coverage of this central
coast meeting can be found here over the next week.
Labels: Bagrada Bug, Bonipak Conf. Room, Heather Scheck, Lisa Blecker, Santa Maria Vegetable Meeting, Steve Koike, Surendra Dara