March 2021 - 18

PLANT HEALTH
Managing
LIGHT &DISEASE
BY ERICA HERNANDEZ
Many variables play a role in disease control, but how can you use lighting technology
as part of your overall strategy?
G
reenhouse production allows growers
the freedom to grow year-round. Though
these structures are controlled and
mostly protected from outdoor environments,
seasonal trends still exert some influence on
crop growth. During winter months, conditions
such as shorter days, lower light intensities
and falling temperatures can contribute to a
disease-promoting environment. Diseases, such
as Botrytis blight and downy mildew, can begin
to creep in.
Growers should take advantage of all available
tools to combat these issues. Using sanitation
and environmental management practices
is well understood, but how can lighting
technology help? The use of supplementary
18 MARCH 2021 GPNMAG.COM
lights increases light intensity, extends
daylength or provides night interruption for
photoperiod control and can provide extra heat.
All of these variables play important roles when
discussing disease control. This article will
examine in detail how these strategies provide
disease control assistance.
DOWNY MILDEW AND BOTRYTIS
BLIGHT
Downy mildew diseases are caused by a
variety of fungal pathogens. This group of
diseases affects important CEA crops such as
basil, spinach and cucumber. Mild chlorosis,
or yellowing, of the leaves often serves as the
first sign that downy mildew has infected a
plant. Soon afterward, sporangia, or sporeproducing
structures, appear on the undersides
of leaves, and chlorotic patches can darken to
purple or dark brown. Systemic symptoms may
also manifest as general stunting and foliar
distortion.
Downy mildew devastates crop yields and
quality. While downy mildew of basil thrives in
warmer conditions, many other disease-causing
species can thrive in conditions commonly
encountered in the fall and winter such as
cool, wet environments. These conditions help
promote the germination, growth and spread
of this disease. Host-specific inoculum are
ubiquitous in the environment, so disease
prevention is key.

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March 2021

Table of Contents for the Digital Edition of March 2021

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