September 2022 - 13

Researchers at the Cal Poly Strawberry Center are studying the effects of UVC
light on strawberry pests. This autonomous equipment from TRIC Robotics applies
the light on strawberry plants at night, and the cumulative effects of multiple
doses of the light kills certain pests.
been working on using ultraviolet-C
radiation (UVC light) to eradicate
strawberry pests in the field. The UVC
radiation has been used for decades to
slow the spread of bacteria.
While her research falls under
entomology and not automation, the
equipment used to apply the light
being used by growers in the area
autonomously roam the fields at night.
She's working with growers who have
contracted with two robotic companies,
Saga Robotics and TRIC Robotics.
Some basic facts on insects and UVC:
* All organisms including insects
have a natural repair mechanism
that activates during daylight to
repair damage done by ultraviolet
light.
* A repair enzyme absorbs natural
light from the sun to obtain
energy for the repair processes.
* For UVC to be effective in
damaging insects it must be
applied only at night.
* Different stages of insects may
react differently to different
dosages of UVC.
* Understanding the dose of UVC
required to damage different
species while not disrupting the
plants' ability to thrive is critical.
Zukoff and graduate student Jose
Alvarado Rojas, who presented the
work at the field day, are focusing on
what UVC dosage range should be used
to kill two spotted spider mites, lygus
bugs and spotted wing drosophila,
which are common pests in California
strawberry fields.
The study started in 2021 and
continues to Summer 2023. Although
all of the data to date hasn't been
analyzed, Zukoff said the process
seems to work best with spider mites
and whiteflies. The dosage needed to
kill adult spotted wing drosophila and
young lygus bugs, however, seems
to be too high for use in strawberry
crops, which can be damaged by too
high of a dosage.
" I know that if you spend too much
time with UVC on the plants it can be
detrimental, " Zukoff said. " There's a
fine line between helping the plant and
hurting the plant. "
The UVC radiation is like a
sunburn, and the cumulative effect of
repeated treatment kills the pests. At
first, the growers were disappointed
that each pass in the field didn't leave a
trail of smoking black dots.
" That's not what happens. It's like a
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Shashika Hewavitharana, assistant
professor and strawberry plant
pathologist at the Cal Poly Strawberry
Center, presents information on
strawberry health at the Cal Poly
Strawberry Center Field Day.
sunburn that gets worse and worse as
time goes by, " she said. " It's not a bug
zapper, it's not an overnight solution.
The point is to keep the insect pressure
lower over time. "
One of the goals of Zukoff and
others testing UVC as a pest killer is
that a successful program could lower
dependence on synthetic pesticides.
Although partnering with growers
who are contracting with the robotic
companies allows strawberry
researchers to learn about what works
without a large expense, it also takes
away the ability of use a control group,
which gives researchers another data
set to work with.
" We have the UVC treatments, and
then we have that compared to the
growers' standards (in the fields not
treated by UVC), but we never have
a full-on control group, " Zukoff said,
because that would require growers to
withhold treatment and lose part of
their crop.
Zukoff's group is also testing UVC
light effects on the pests inside a
Strawberry Center lab to back up
what's happening in fields.
The research will continue through
summer 2023, and the results will
be analyzed, along with information
from a similar study at the University
of Florida.
" Between their lab and our lab,
hopefully we'll be covering most of the
pests on strawberries and there won't
be a lot of unanswered questions, "
Zuckoff said. " Then it will be up to
the growers. " FGN
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September 2022

Table of Contents for the Digital Edition of September 2022
