BASF - 2019 - 8

Preventing and managing
devastating potato late
blight outbreaks
Photo by Peter Wong
L
ate blight can rapidly become
severe; farmers can see it
go from a few lesions to
complete defoliation in just a few
days. When vines are destroyed,
photosynthesis is stopped and
yield is dramatically impacted
since tubers can be affected.
In order to manage this disease
before it causes serious damage
to a crop, potato farmers can be
proactive and scout for signs of
the disease on their own. Farmers
should start to scout as soon as
the crop starts to emerge. Certain
areas of a field tend to be more at
risk than others. Farmers should
look for lesions in low spots,
compacted areas, rows close to
tree lines, field edges along creeks
or ponds, pivot center points, pivot
wheel tracks and weedy areas of
their fields.
In addition to scouting for
the disease in their fields,
Curtis Rainbolt, Technical
Service Representative at
BASF, recommends farmers
use a proactive application of
a fungicide, such as Forum®
fungicide, to control this disease.
Forum fungicide should be
tank-mixed with multisite
inhibitors. The multisite inhibitors
are slightly less effective,
but since they have a lower
potential for resistance, applying
chemicals such as chlorothalonil
or copper in combination with
8
Spudman
Forum fungicide will help with
resistance management.
" When conditions are favorable
for late blight development,
multiple applications up to more
than once a week might be
necessary. As a result, resistance
management is often difficult, "
said Rainbolt. To mitigate this,
farmers should rotate chemistries
and avoid pairing chemistries
from the same FRAC group
together.
" Forum fungicide is ideal
for prevention and control of
late blight because it greatly
reduces sporulation of the
disease, " Rainbolt said. Forum
fungicide " disrupts fungal cell
wall formation by interfering with
cellulose synthase, " he explained.
In layman terms, it devastates
fungal cell walls and prevents
them from repair.
Rainbolt recommends that
farmers review the rate structure,
but that they do not reach the
maximum allowed application.
" 5.5 ounces in combination with
a multisite inhibitor will work
most effectively. Forum fungicide
has good activity on late blight.
However, we need to be aware of
resistance management for late
blight, so be sure to mix multiple
FRAC codes, " he said.
Above all else, late blight is a
community disease. Farmers can't
simply rely on their own good
habits and correct chemistries to
prevent the devastation that late
blight can cause to a crop -
cultural practices are also
important. " Often late blight is
worse in years when we have a lot
of volunteer potatoes. If late blight
survives the winter in volunteer
potatoes or cull piles, the disease
is often worse the following year, "
Rainbolt said.
To prevent late blight from
devastating crops, it is vital for
farmers to work with their local
university extension program, as
extension personnel track late
blight very closely. When farmers
call the extension about late blight
lesions, and once late blight is
confirmed in fields, the university
will issue an alert to the area.
By working with university
extension programs and
communicating with neighboring
farms, farmers can help a region
stay isolated from an outbreak
of late blight. Pairing this
communication with proper
cultural practices and the right
chemistries, such as Forum
fungicide in a tank mix, will go
a long way in preventing the
devastation that late blight can
cause to potato farms.
For more information, visit
GrowSmartPotatoes.com
or contact your local BASF
representative.
Always read and follow label directions.
Forum is a registered trademark of BASF. © 2018 BASF Corporation. All rights reserved.
http://www.GrowSmartPotatoes.com
BASF - 2019

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