Almond
PMA Newsletter Summer 2001
This
newsletter is published with funds
provided by
the California
Department
of Pesticide Regulations.
The Almond
Pest Management
Alliance (PMA)
project is designed to
promote a
reduced risk system of
almond
production through the use of
alternative
products, actual on-site
demonstrations,
and grower education.
The PMA
partners include: the
Almond Board
of California, the
Almond
Hullers and Processors
Association,
the UC Statewide IPM
Project, UC
Cooperative Extension
farm
advisors, and the Community
Alliance
with Family Farmers.
The Missing Moth Mystery
This
is the story of a moth that is rarely a pest in almonds, but one that
drew some
attention for its activity in PMA almond orchards during the
2000 growing
season. As we move away from traditional spray programs to
reduced-risk,
or "softer" pest control strategies, we might expect to see the
emergence of
pest populations that were not previously a problem. Minor
pests that
were once held in check by broad-spectrum pesticides may not
be apparent
in orchards until we cut back on those sprays. We may need to
adjust our
control strategies as these pests show up, or it may just take a
few years
for natural
enemies to
build up in
our
"soft approach"
orchards.
One
likely suspect in
this
transition is the
obliquebanded
leafroller.
It can be
mysterious
to almond
growers
because the
damage it
can cause is
not always
easy to
detect.
Frank Zalom,
director of
the UC IPM
program,
told a group
of growers
and PCAs at a spring PMA field day in Hickman that OBLR
damages
almonds during the spring, in its first generation. However, that
damage is
rarely, if ever, accounted for at harvest. OBLR overwinters in a
larval
stage, protected in a silk hibernaculum. Upon emergence, OBLR will
web leaves
together and begin feeding. In the spring, OBLR will eat
watersrpout
shoots and will move on to nutlets. The caterpillar will hollow
out nutlets,
which then fall to the ground by the June drop. The later
generations
of OBLR are unable or unwilling to get into the nut as it
matures, so
it is never seen in the fall crackout or reported on a gradesheet.
Roger
Duncan, Stanislaus County Pomology Farm Advisor, said he saw
OBLR all
over the PMA demonstration orchard in the 2000 growing
season. In
2001, Roger, Frank, and Walt Bentley, Area IPM Advisor, set
up trials at
the ranches of Rod and Connie Hooker and of Brent Stout to
look at the
control of this emerging pest. Oddly enough, this didn't turn
out to be a
very good year for OBLR and three minute searches of
untreated
orchards turned up an average of less than five OBLR nests.
Stanislaus County farm advisor Roger Duncan shows PMA
field day participants how to identify OBLR damage at Rod and Connie Hooker's
ranch in Hickman.
Interestingly,
PCAs have reported typical OBLR
levels in
peach orchards this year, leaving almond
growers and
researchers to wonder why the moth is
passing on
the nuts.
The trial
did return useful results for growers
facing
significant losses from OBLR. The research
team applied
10 different treatments to the orchards.
These were
dormant and spring sprays of various
materials
including Supracide (dormant only),
Pounce
(dormant only), Success, Confirm (an insect
growth
regulator, registered in almonds this year), and
Bt. The
bottom line is that dormant sprays reduced
populations
of OBLR, but not as well as the
springtime
sprays. The best performers were Success
at petal
fall (March 12, in this case), Bt at petal fall
and nine
days later (at about 80% PTB emergence),
and Confirm
at petal fall.
While
there are no established economic thresholds
for
OBLR, good observation will alert you to their
presence and
you may have the opportunity to
become more
familiar with this insect.
Peach Twig Borer
Biology
By Joe
Connell, UCCE Farm Advisor
, Butte
County
Peach
twig borer adult moths have gray mottled
forewings.
Females lay eggs on shoots, fruit, and leaves.
Eggs hatch
in 4 to 18 days. Larvae are small, brown
caterpillars
with white bands and a black head capsule.
They go
through four to five growth stages. Pupae are
dark brown,
without a cocoon and are found in tree
bark
crevices, between hull and shell, or in debris on
the ground.
They have four generations per year.
Larvae
damage growing shoots, particularly a problem
in the
spring on first-and second-leaf trees. When
feeding on
nuts after hullsplit, they cause shallow
surface
grooves on the kernel.
In
bearing orchards, the preferred time to treat
peach twig
borer is usually during and shortly after
bloom with
well-timed treatments of Bacillus
thuringiensis.
This timing has the least negative impact
on the
environment and natural enemies. Resistance of
peach twig
borer to pyrethroids has been identified in
some areas
of Butte County.
Control
of peach twig borer during hullsplit is
difficult.
Timing is critical for good control and sprays
should be
applied at 1% hullsplit to target hatching
larvae of
the second generation. If larvae are present
right when
hulls split, they may feed in the hull and
move into
the nut. If the bulk of the second generation
hatches
before hullsplit, they will primarily feed
on shoots
and miss the crop. If they hatch well after
hullsplit
and kernels have begun to dry, they are less
attractive
to PTB and damage may be avoided.
In
first-and second-leaf orchards, May sprays for
peach twig
borer are recommended when peach twig
borers are
present because young trees are attractive to
the pest and
resulting injury could damage developing
scaffolds
and disfigure the tree. Pheromone traps and
degree-days
can help time a May spray. Peach twig
borer
pheromone traps should be placed in orchards by
March 20.
Optimum timing for first generation larvae
(the May
spray) is between 400 and 500 degree-days
after the
first male is trapped in April.
The San Jose Scale in Southern San Joaquin Valley
By
Mario Viveros, UCCE Farm Advisor
, Kern County
The
San Jose Scale is a key pest in almonds. It feeds
on plant
juices and, at the same time, injects a toxin
that
contributes to twigs and limb death. In 1996,
there were
major flare-ups of San Jose Scale in the
Southern San
Joaquin Valley.
James
R. Brazzle, former Kern County Entomology
Farm
Advisor, (Kern Almond News, December, 1997)
lists
factors that may have contributed to these flare-ups:
1)
mild winters increase survival of overwintering
scale,
2) in-season insecticide use and dusty conditions
decrease
biological control,
3) biological control alone
may not
reduce scale below economic levels,
4) dormant
spray
applications for San Jose Scale control are
needed a
minimum of every second year,
5) dormant
spray
applications provide greater scale control and
delayed
dormant applications provide peach twig borer
control, and
6) resistance to organophosphates may impact
control. At the present time, we are studying
what, if
any, impact these factors have on the population
dynamics of
San Jose Scale in the PMA orchard in
Kern County.
The
conventional dormant spray of 1999 consisted
of five
pints of Diazinon‚ and six gallons of oil in 200
gallons of
water per acre. The trees were sprayed on
January 4.
In 2000, we changed the conventional
three pints
of Lorsban‚ and four gallons of oil in 230
gallons of
water per acre, due to low chilling hours and
dry winter.
We applied the 2000 dormant spray on
January 17.
The conventional dormant spray in 2001
was applied
on January 23, using five pints of
Diazinon‚
and six gallons of oil. We left the reduced
risk
treatment unsprayed in 1999. Then in 2000 and
2001, we
sprayed the reduced risk treatment using six
gallons of
oil in 200 and 230 gallons of water respectively,
using the
same spray timing as the conventional
treatment.
We
used three methods to monitor San Jose Scale.
The sticky
traps with pheromone-loaded rubber septa
were used to
monitor the adults. To monitor crawlers,
we attached
double-sided sticky tape to limbs. Fruiting
spurs were
used to determine infestation on the tree.
In addition,
we tracked two parasitoids in the orchard:
Encarsia
perniciosi and Aphytis.
The
data on male flights on both conventional and
reduced risk
showed no differences. Furthermore, the
Encarcia
populations were identical in both management
systems.
However, the crawlers in the reduced
risk were
more abundant than on the conventional
management
system.
The
percent of infested fruiting spurs by San Jose
Scale are
shown in the table below. It is clear that the
percent of
infestation from 2000 to 2001 increased in
both conventional and reduced risk treatment, and
that the
reduced risk treatment showed a greater
overall
percentage of infestation than the conventional.
This latter
result may be due to a lack of dormant
spray in
1999.
From
the data, we conclude that dormant sprays are
necessary in
the Southern San Joaquin Valley for the
control of
San Jose Scale. Also, organophosphate
insecticides
do play a role in the control of this insect.
"Soft
" Programs are working in
Stanislaus
County
By Roger
Duncan, UCCE Farm Advisor
, Stanislaus
County
The
Stanislaus County PMA trial will continue into
the third
season with treatments similar to the first two
years. Those
treatments are summarized in the Fall
2000 Almond
PMA Newsletter, and described in detail
on the PMA
Web site.
After
two years of intensive monitoring, we have
not seen an
increase in any pest in the "soft" treatments
compared to
the standard grower's practices. There
also have not been any differences in rejects due to
PTB or NOW
at harvest. It is clear San Jose Scale
parasitoids
are significantly reduced in areas where a
pyrethroid
is applied in the dormant period and an
organophosphate
is applied in-season. In Stanislaus
County,
almond and stonefruit orchards rarely have
significant
damage from San Jose Scale whether orchards
are treated
with insecticides or not. However,
in areas
where San Jose scale is a serious threat, growers
should
understand that the use of some insecticides
could
exacerbate their scale problems.
The
cost of the Bt program is almost identical to
the grower's
standard pesticide program if it can be
included in
normally scheduled fungicide sprays. If
pyrethroid
or organophosphate sprays cause an increase
in mites and
thus necessitate a mite spray, a Bt program
could prove
to be more cost effective. The intermediate
treatment is twice as expensive as the
other two
programs. The costs of Success and Agrimek
exceed their
alternatives. In addition, Agrimek must be
applied
early in the season as a preventative treatment,
often
leading to unnecessary applications.