JANUARY | FEBRUARY 2017
Almond Facts
45
pressure the following year. Rijal also does mummy nut
sampling. “This is important to do given that NOW is
becoming more of a problem,” he said. He encouraged the
audience to develop orchard histories of NOW damage
on their ranches: “Once there is insect pressure it tends to
continue in following years, so orchard histories play a very
important role in navel orangeworm management.”
The farm advisor begins placing egg traps in March/April
to establish a biofix – the date at which the NOW moths first
emerge from pupation and begin flying to lay eggs on the
nuts. When 75 percent or more of the traps have increased
egg counts in two consecutive weeks, the team establishes
that date as the biofix date and begins counting the degree
days to calculate when to begin pest management. In 2016,
egg traps placed in early April had egg counts high enough
to establish April 18 as the biofix. At 100 degree days, in late
April, the “May” spray would be applied if needed, based on
insect activity. At 1200 degree days, the first week of July, the
hullsplit spray would be applied, if needed.
Pheromone Traps
Pheromone traps contain the female sex hormone –
pheromone – to attract male moths. These traps provide
information about adult flight activity and identify peak
flights. They are more useful in making hullsplit treatment
decisions, Rijal observed. The egg traps may not attract
a representative sample of females because they have the
option of laying eggs on almonds already at hullsplit.
The combination of the two types of traps gives a better
indication of NOW populations and activity.
Harvest Samples
Harvest samples enable growers and their PCAs to identify
the types of insect damage occurring in an orchard,
whether it is from NOW, peach twig borer, Oriental
fruit moth, ants, leaffooted bugs or some other pest. Rijal
recommends a minimum sample of 500 nuts. The findings
can be important in planning management and control
programs, he said.
Management Options
Rijal noted that two management practices stand out as
the most effective in reducing NOW damage. He cited (1)
orchard sanitation –
removing mummy nuts
, and (2)
early harvest. He recommends no more than one mummy
per tree, being certain the mummies are removed from the
trees by February 1, and flail mowing or discing by March
1 to remove the mummies from the ground. The moths will
lay eggs on mummies left on the ground causing significant
damage to the crop.
By
early harvest
, he means harvesting before the 3
rd
generation eggs hatch, and when 100 percent of the nuts
at the six- to eight-foot level are at hullsplit.
Insecticide control
, he said, is a help and can reduce
NOW damage by 50 percent. For example, if a grower
does not use insecticide and gets 4 percent damage, but
had used an insecticide he would have reduced the damage
to 2 percent.
Mating disruption
is a new technique under investigation
that may have applicability in the future. It involves
releasing female pheromone in the orchard to confuse the
males seeking a mate. Two companies are producing the
material at present and others are testing their compounds
for registration. The technique involves a container hung in
trees that periodically releases the pheromone to confuse the
male insects. Data is still being collected to determine the
effectiveness of this approach.
Insecticides
Many new chemicals are available that are very effective,
Rijal reported, and also are less problematic for other insects,
such as mites. Some chemistries used in May will cause an
outbreak of mites, he said. He advises using egg trap data
and the 100 degree day regimen for optimum timing of
the May spray. And encourages using a “soft’ or reduced-
risk material. He cited Intrepid, Altacor and Proclaim, for
example. He mentioned Delegate and Entrust, but noted that
those chemistries are harmful to bees.
For hullsplit spray he again suggested using egg trap data and
the 1200 degree day measurement from the spring biofix. He
cited Intrepid, Delegate, Entrust, Altacor, and Proclaim as
possible choices along with other products listed on the UC
IPM website.
The critical issue with insecticide use, he said, is
spray
coverage
. Poor spray coverage and lower NOW control
occurs in the upper quarter of the tree canopy – above 10 feet.
He suggests tractor speed of two miles per hour and higher
spray volume (200 gallons per acre) for best NOW control.
Needs Volunteers
Rijal invited growers to join a demonstration study in
Stanislaus and Merced counties that is comparing IPM
control to a grower standard regimen. The study will focus
on NOW, PTB, Leaffooted bug, ants, scale and mites.
Participants will need to be willing to use mating disruption
materials. Ideally each block should be about 100 acres, he
said. Contact Jhalendra Rijal,
.
