May 2019 - 6

Wet season challenges growers in eastern US
By Stephen Kloosterman
Associate Editor
Growers from Wisconsin to
Pennsylvania are hoping for sun this
summer after rainy days during 2018
led to trouble with plant disease and
lower yields.
It was an above-average year for
precipitation from the Great Plains to the
Atlantic Coast, according to the National
Weather Service's annual report.
Wisconsin Potato & Vegetable Growers
Association blamed the wet year for a 12
percent decline in its potato crop, and
the East's precipitation was even more
extraordinary. Pennsylvania was one of
nine states that experienced " their wettest
annual period on record, " according
to the National Weather Service. The
others were Tennessee, North Carolina,
Virginia, West Virginia, Maryland,
Delaware and Massachusetts.
Penn State University vegetable
pathologist Beth Gugino kept busy
diagnosing different outbreaks for
growers, related to the wet weather.
Gugino discussed disease management
during three education sessions at
January's Mid-Atlantic Fruit and
Vegetable Convention in Hershey,
Pennsylvania. Growers at the convention
often joked often about the dismal
growing conditions of the past year.
Fungal diseases in tomato leaves, head
develop on the plant's lower leaves and
then work up - it's encouraged by wet
and warm temperatures.
Fruit rots can come later in the
season - caused by early blight fungi
in addition to other species: Alternaria
alternata and colletotrichum.
Head rot in broccoli
Gugino said that there has been an
increase in broccoli and cauliflower
acreage across the region, and the rain
led to an increased number of " head
rot diseases. "
" In general, head rot is characterized
A flooded onion field in Pennsylvania. Photo: Beth K. Gugino
rot in broccoli and cauliflower, and vine
crop disease management were all areas
of concern that Gugino spoke about at
the convention.
Vine crop concerns
Gugino said the weather also made
it difficult to seed, transplant and
spray fungicides.
" To say that this year was a minor
challenge was really an understatement, "
she said. " I think we really struggled,
especially in our vine crops, producing
any types of yield, and also producing
high-quality yield. "
Plants can usually live in waterlogged
soils for up to 48 hours, but longer than
that and the plant roots begin shut down,
she said.
Gugino gave a few mitigation strategies
for the growers:
* Avoid working wet soils if
possible, especially fine-textured
soils that compact easily.
* Replenish nutrients that may
have been leached either by sidedressing
or fertigating.
* Use a subsoiler between beds to
break up layers of compaction,
especially if exposed to heavy
traffic.
* Consider row orientation and if
cutting drainage channels at the
end of rows would help.
* Plant or mulch row middles to
reduce potential erosion.
" Diseases are exacerbated in wet
weather, " she said. " I wish I could tell you
one that really isn't. Bacterial diseases
obviously - I mean they are really
spread by rain splashing ... fungal foliar
diseases, fruit rots and root rots, they're
going to be exacerbated by the wet
weather we're going to be having. "
Curbing diseases
Gugino cautioned growers against
carelessly spreading fungi around the
farm. For instance, if there is a fungal
infection in the field, but not in the high
tunnels, it might be a better strategy
to start the morning working in the
tunnels and then move to the field -
rather than vice versa.
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6 | VegetableGrowersNews.com
equipment. One way to avoid
transferring disease is disinfecting
tomato stakes between crops. A more
extreme example given at the conference
was using a different disposable razor for
trimming each plant.
A three-year crop rotation between
different vegetable families is also a good
practice to prevent a serious problem
from holding over from year to year.
She also encouraged growers to be
familiar with when and where diseases
are likely to develop.
Some of the usual suspects include
early blight and septoria leaf blight.
Early blight is often caused by Alternaria
solani, and appear as small, brown-toblack
circular lesions that may develop
yellow chlorotic spots. Symptoms often
by water-soaking and discoloration of
individual or small groups of florets, "
according to a Gugino paper published
in the convention proceedings. The
conditions are made worse by moisture
on the florets.
But defining the type of disease can
also be a big help.
Bacterial head rot starts with little
soaked spots on the immature florets
where the water collects. As time goes
on the areas can become necrotic and
turn black or brown. Ways to avoid
bacterial head rot include choosing a
variety that has
dome-shaped,
rather than
flat heads, and
cultural practices
that help the
plants dry off
with better air
circulation.
Black rot
is caused by
the bacterial
BETH GUGINO
pathogen
Santhomonas capestris. Symptoms
usually first are seen at leaf edges. Leaf
lesions often are yellow and V-shaped.
Copper is the primary management tool
for broccoli already transplanted in the
field, but Gugino said the emphasis needs
to be on growing transplants in a clean
area, and selecting healthy transplants.
Downy mildew is caused by an
oomycete, or water mold pathogen called
Hyaloperonospora brassicae. Outbreaks
are common in the fall in the MidAtlantic
region. Purple and yellowishbrown
lesions develop on the upper leaf
surface. Some fungicides are available for
downy mildew, and crop rotation and
plowing plant residue can prevent the
pathogen from surviving between crops.
Alternaria leaf spot and head rot is
caused by a fungal pathogen. Lesions
on leaves start as small dark spots that
expand to two- or three-inch concentric
rings, according to Gugino. Infected
heads of broccoli and cauliflower have
small black or brown spots.
Many of the cultural practices
recommended for the other diseases will
also help to manage Alternaria leaf spot,
she wrote. " Some research has shown
that mulches and other barriers that
reduce soil splash can help with disease
management. Protection of the broccoli
and cauliflower heads is important
especially once symptoms are observed
in the field. " VGN
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May 2019

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