IN YOUR ORCHARD
AF36 to Reduce Aflatoxin within Almonds
Aflatoxin is a carcinogen produced by a strain of the
fungus Aspergillus flavus. Due to the potency of this
toxin and its occurrence within almonds, there are very
low regulatory limits within consumer markets to reduce
human exposure. This pathogen infects nuts at the onset
of hull-split and has a very close association with NOW
infestation. Recent work has found that a competitive
Aspergillus flavus strain that does not produce the
toxin can outcompete the toxigenic strain in the
orchard environment. This strain has been commercially
developed into a product and made available for field
application. To be effective within almonds, 10 pounds
per acre of inoculated grain should be applied one to
two weeks prior to hull-split into the irrigation pattern
of the field. Irrigation is required after application. With
the application of this product, research has shown a
40 percent reduction in aflatoxin producing strains within
almond kernels.
Ants
Fire ants and pavement ants are serious problems
where they are present. If in high populations, they can
consume between one to two percent of the crop within
four days. Fields should be scouted in mid-May and
monitoring and treatment information can be found
within the UC Almond Pest Management Guidelines
(
).
Baits containing growth regulators, if needed, should
be applied one month prior to harvest for maximum
effectiveness. If bait wasn't applied, a broadcast spray
of organophosphate should be applied as close to
harvest as allowed to reduce foragers. Recently, a new
reduced
–
risk bait with a shorter pre-harvest interval
was approved for almonds with the active ingredient
metaflumizone. This product can be applied later in the
season and has been shown to reduce problematic ant
populations. To further reduce ant damage, nuts should
be picked up as soon as possible after shaking.
Be mindful that not all ants present within the orchard
feed on almonds. A quick trick to distinguish “good ants”
from “bad ants” is to throw potato chips or a hot dog
near the mound. If consumed, it can be assumed that the
colony will also feed on almond kernels. Another trick
is to stomp near the mound to bring ants to the surface.
If they swarm out of the mound, are red in color with a
black butt and bite, they are most likely fire ants. Be on
the lookout for red imported fire ants, which are being
found in more areas – it is likely these ants may damage
crop at a higher level than native fire ant populations.
Webspinning Spider Mite Management in
Almonds
As temperatures increase, monitoring for webspinning
spider mites should occur. The most common species
during the summer are Pacific and twospotted spider
mites, though on occasion strawberry spider mites can
be found. As adults, all three mites look and behave
similarly, even though Pacific spider mites are more
difficult to control.
In controlling spider mites, the most important factor is
biological control. When natural enemies are abundant,
miticides are not needed. When natural enemies are
absent, control with even the best miticides can be short-
lived. The goal is to find a balance that relies primarily
on natural enemies supplemented by miticides as needed.
Growers who want to conserve and promote predators
should avoid broad spectrum insecticides, particularly
early in the season, and avoid prophylactic and
preventative miticide applications that do not provide
enough food for mite predators to become established in
the spring.
In determining when to time the first mite spray
application, a presence/absence monitoring protocol
has been developed. Monitoring should occur weekly,
and prior to mid-June should focus on hot-spots within
the orchards. After mid-June, the whole orchard should
be randomly sampled. When sampling trees, 15 leaves
from a minimum of five trees should be selected. Leaves
should be randomly chosen from the inside and outside
of the canopy. Examine both sides of the leaves looking
for pest mites and predators. Note the number of leaves
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A L M O N D F A C T S
