September/October 2024 - 28

VEG CONNECTIONS
Advancing onion thrips management
Innovations and latest research insights
BY NATALIE CONSTANCIO
AND ZSOFIA SZENDREI
T
he Vegetable Entomology
Laboratory at Michigan
State University has been
conducting research on onion thrips
management in onions for 15 years.
During this time, we have initially
focused on developing insecticide
programs to prevent thrips from
becoming resistant to insecticides.
Updated insecticide
program recommendation
The most up-to-date
recommended insecticide program
starts with two applications of
Movento (Bayer, spirotetramat),
seven days apart, applied at
0.5-1 thrips per leaf threshold.
This is followed by various other
insecticides with different modes of
action, applied at a threshold.
The threshold to apply insecticides
is 1 thrips/leaf for most insecticides,
except Radiant (Corteva, spinetoram)
which is 3 thrips/leaf. The most
effective insecticide currently
available for thrips control is Radiant,
it is recommended that this product
is used when thrips populations
are the highest, usually in late July
in the Midwest.
In our research, there have been
many years when we only needed
two Movento and two Radiant
Don't just plant
it and think you're going
to sell it. Understand your
marketplace and your
consumers who in today's
world are changing. "
28 | SEPTEMBER/OCTOBER 2024
Figure 1: A) Larval onion thrips in the neck of an onion plant. B) Symptoms
of multiple plant pathogens on onion foliage. Photos courtesy of MSU.
applications for the entire growing
season to keep thrips below the
economic threshold, thus the use
of thresholds can be crucial for
minimizing insecticide applications.
Onion thrips and
fungal pathogens
More recently, our lab has been
interested in how onion thrips and
fungal pathogens of onion interact
with each other (Figure 1). We
found that onion thrips preferred to
reproduce and spend time on plants
that were infected with a fungal
pathogen over healthy plants.
Our next question was: " How are
thrips contributing to onion pathogen
spread? "
We determined that the more
thrips there are on plants, the more
the pathogen spreads from one plant
to the next; thus thrips suppression
can be important for reducing onion
fungal diseases. We also learned
that at high temperatures, thrips
reproduced at a higher rate and
moved more between plants leading
to increasing pathogen spread.
While thrips contribute to
spreading onion fungal pathogens,
they are not the sole spreaders of
pathogens in the field, many of them
are spread mechanically. Therefore,
fungicides are still necessary for
managing pathogens in onion fields.
However, our research suggests
that by reducing thrips, especially
in those years when pathogens are
problematic, there may be additional
benefits of reducing onion thrips for
keeping onion foliage healthy longer
(Figure 2).

September/October 2024

Table of Contents for the Digital Edition of September/October 2024

Editor's Letter
Accelerated deadline
Weeding out danger
East Coast diversification
Regenerating soil
Connecting innovation and education at the Great Lakes EXPO
Organic Grower
Veg Connections
Farm Market & Agritourism
Ag Labor Review
Classifieds
Advertiser Index
September/October 2024 - 1
September/October 2024 - 2
September/October 2024 - 3
September/October 2024 - Editor's Letter
September/October 2024 - 5
September/October 2024 - Accelerated deadline
September/October 2024 - 7
September/October 2024 - Weeding out danger
September/October 2024 - 9
September/October 2024 - 10
September/October 2024 - 11
September/October 2024 - East Coast diversification
September/October 2024 - 13
September/October 2024 - 14
September/October 2024 - 15
September/October 2024 - Regenerating soil
September/October 2024 - 17
September/October 2024 - Connecting innovation and education at the Great Lakes EXPO
September/October 2024 - 19
September/October 2024 - 20
September/October 2024 - 21
September/October 2024 - 22
September/October 2024 - Organic Grower
September/October 2024 - 24
September/October 2024 - 25
September/October 2024 - 26
September/October 2024 - 27
September/October 2024 - Veg Connections
September/October 2024 - 29
September/October 2024 - Farm Market & Agritourism
September/October 2024 - 31
September/October 2024 - Ag Labor Review
September/October 2024 - 33
September/October 2024 - Classifieds
September/October 2024 - Advertiser Index
September/October 2024 - 36
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