April 2022 - 15

Left, Carrie Wohleb, a Washington State University regional vegetable crops specialist,
speaks about smoke effects on potato plants. Right, University of Idaho Professor and
Extension specialist Mike Thornton addresses the topic of heat stress on potatoes.
Photos: Bill Schaefer Photography
She cautioned to be mindful of
environmental changes created
by smoke combined with weather
conditions when managing your crop.
" During smoky haze, for instance,
you might find that the crop needs
less water and you should irrigate
less, " she said.
Smoky conditions sometimes play
positive roles in plant development,
Wolheb said.
" The CO2 from smoke is not
really a negative factor, and it might
even be a positive factor as long as
low light from smoke is not limiting
photosynthesis first - that's that
law of limiting factors, " she said.
" Temperatures are often moderated
when there's smoke. So, for many
crops the smoke cover may actually
be a positive factor if it helps to cool
things down when it would otherwise
be really hot out. "
The proximity to wildfires makes a
big difference in the impact on the crop.
" The closer you are to those fires,
usually the bigger difference it
makes, " she said.
HEAT STRESS
Mike Thornton, professor of plant
sciences with the University of Idaho,
followed Wohleb with a presentation
on the continuing impact of heat
stress on potato crops during the past
decade, with special emphasis on the
impact to the 2021 potato crop.
" Here's the main message, "
Thornton said, " it would be great if
we could just say, 'hey, yeah, heat's
bad for potato growth and therefore
yields are down,' but it's way more
complicated than that. "
The problem is not limited to
heat stress, it's about water uptake,
irrigation management and how to
supply plants with necessary nutrients.
Potatoes are a cool-season crop that
best thrive when temperatures are in
the mid-70s during the day and mid50s
at night, similar to conditions in
the Andes Mountains, where the crop
originated. Potatoes adapt somewhat
to warmer temperatures, but it's
continuous high temperatures that
damage the plants.
" If we have a day or two of hot
temperatures, (there's) very little
impact " Thornton said. " If we have five
to 10 days where it's 95, 100 degrees,
that really starts to hurt the crop. "
High heat complicates every other
decision potato growers make.
" I like to think of it as your margin
for error. When it's hot you don't
have near the margin of error in
your irrigation management, you
don't have near the margin of error
in your nutrient management, in
your pest management, everything
else becomes more critical because if
you add one of those stresses to heat
stress than you really get in trouble
real quick, " Thornton said.
The focus on the impact of heat
stress on potato plants has become
even
more
important
with
heat
indices projected to continue rising
throughout the 21st century.
According to the U.S. Fish and
Wildlife Service (USFWS), the average
temperature in the Pacific Northwest
Spudman * April 2022
13
April 2022

Table of Contents for the Digital Edition of April 2022
