84 POTATO GROWER | JANUARY 2017
harristonmayo.com
Idaho Falls
Todd Geyer
(208) 520-7049
Phil Browning
(208) 520-4837
Speed Clean
Surge Hopper
Receiving/
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Clodhopper
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160691MayMfg12h.indd 1 6/1/16 8:47 AM
is present between canopy closure and
harvest. Forecasts for rain are beneficial in
scheduling fungicide applications for late
blight management in the Columbia Basin.
The management strategy in the Columbia
Basin is, naturally, to initially keep late
blight out of fields. Once inoculum is in
a field, the disease is extremely difficult
to manage. For example, late blight
incidence increased from 0.6 to 70 percent
in 35 days in a field of Russet Norkotah
even with nine fungicide applications
being made during that time period.
Initial inoculum for this field originated
from infected seed tubers.
Ultimately, fungicide applications for late
blight before row closure in the Columbia
Basin are likely not warranted unless a
prolonged rainy period is expected. In
that case, fungicides can be effective
in protecting foliage from infection
by sporangia that could be potentially
produced on latently infected potato
shoots arising from infected seed pieces,
and possibly from other inoculum sources
such as infected refuse tubers and infected
volunteer potatoes.
After row closure, temperatures during humid
periods are often favorable for late blight infection.
