March 2020 - 16

Managing pepper diseases requires layered practices
By Dean Peterson
VGN Correspondent
Peppers face fewer plant pathogens
than other crops but diseases are still a
big concern.
" Peppers get fewer diseases than
tomatoes but in general they get
hammered harder, " said Sally Miller,
professor in vegetable pathology at
Ohio State University and a speaker at
the recent Great Lakes Fruit, Vegetable
& Farm Market EXPO in Grand
Rapids, Michigan.
Anthracnose was a non-issue in
peppers a decade ago but has emerged
as a major concern. It's favored by
warm, wet weather and the damage
mainly appears on the fruit. " It's
extremely aggressive, " Miller said. The
anthracnose lesions on the peppers
are full of spores that are moved
around by rain or irrigation.
White mold is favored by cool, wet,
humid conditions and can be more of a
problem in hoop houses where there is
less air movement and higher humidities.
Grey mold (botrytis) is favored by
cool, moist, humid conditions. It has
many hosts, produces many spores and
is ubiquitous to pepper production.
Pythium root rot is favored by
saturated soils, kills the roots and
may even spread up into the crown.
" I see the most of this when you
plant peppers into cool, moist soil
Syringae leaf spot has emerged as a
new, seedborne, bacterial disease. " It
looks like bacterial leaf spot, " Miller
said, and is often misidentified.
Transmission tendencies
Virus diseases that affect peppers fall
into two categories - insect-transmitted
and mechanically-transmitted.
Insect-transmitted viruses include the
tosporviruses which are most typically
transmitted by thrips. These viruses
include tomato spotted wilt virus
(TSWV) and impatiens necrotic spot
virus (INSV). Cucumber mosaic virus
(CMV) is another insect-transmitted
virus and is spread by aphids.
Mechanically-transmitted viruses
Anthracnose of pepper. Photo: Ohio State University
and then it gets hot, " Miller said. The
result is moisture stress and stunted,
unproductive plants.
Phytophthora often starts in low spots
or other areas of poor drainage. It's
favored by warm, rainy conditions and
can be spread by contaminated surface
water. It's a long-lived pathogen - both
in the soil and in water.
Bacterial leaf spot is the most
common and most important bacterial
disease of peppers. It's seedborne and
can overcome disease resistance. It's
triggered by hot, moist conditions but is
short-lived in the soil in cool climates.
" The key through all of this is
moisture, " Miller said. " Moisture is the
driver for all of the pepper diseases. "
Bacterial canker is a devastating,
seedborne disease of tomatoes, but
is less common in peppers. It affects
peppers but doesn't kill them and
can be mistaken for other diseases.
Bacterial canker's classic symptom on
peppers is rough, raised spots on the
underside of leaves.
Bacterial soft rot is favored by
warm, wet weather. It infects plants
through wounds and is associated with
insect damage of the fruit.
include the tobamoviruses which
include tobacco mosaic virus (TMV)
and tomato mosaic virus (ToMV).
Tomato brown rugose fruit virus
(TBRFV) is new and also mechanicallytransmitted.
" It was only recognized a
couple of years ago and has turned the
tomato and pepper industries into an
uproar, " Miller said. TBRFV is a very
serious disease that is not present in the
U.S. and has led to numerous USDA
import restrictions (see Vegetable Growers
News, January 2020 issue, page 18).
Integrated approach required
Managing pepper diseases requires
an integrated management program.
Many pepper diseases - especially
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March 2020

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