A2frL*ncaster Farming, Saturday, March 11, 1995
Late Blight Disease Threat Under Gun At State Potato Growers Meeting
(Continued from Pago Al)
potatoes unmarketable.
What makes an outbreak parti
cularly dangerous is that it can eas
ily be generated by next-door
neighbors who grow tomatoes in
gardens. Without constant and fre
quent fungicide treatment, late
blight attacks tomatoes and is
spread by air to potato plants. The
disease can originate in tomato or
potato hosts and can strike either.
Fry showed examples of the
effects of late blight at the Cornell
University research plots in Ithaca,
N.Y. Of the plots shown, late
blight was started Aug. 2 last year
and by Aug. 19, much of the
foliage was gone. “The disease
can increase and spread dramati
cally,” said Fry.
TTic disease can progress from 1
percent of total coverage to total
death in a span of 18-28 days.
What is worse is that good
growing conditions for potatoes
also spell good conditions for the
outbreak and spread of late blight
The fungus was originally
brought to the U.S. from central
Mexico in the late 1830 s and early
1840 s, according to Fry. It was the
primary cause of the Irish Potato
Famine in 184 S. It can readily
spread by air to neighbor fields.
The mating type of the original
fungus was Al, an “asexual”
organism that cannot reproduce
itself. It needs a living host in order
to survive. But more virulent and
longer-lasting mating types
emerged through the years, such as
the A 2 mating type.
What concerns researchers,
according to Fry, is the emergence
of more deadly and longer-lasting
types, the A-7 or A-8 strains,
which can reproduce and may be
extremely difficult to handle. The
new types, isolated in 1992, are
very aggressive, can infect toma
toes and potatoes readily, and are
resistant to commercial
fungicides.
In 1994, US-7 isolates were dis-
DON'T THROW AWAY
OF YOUR HAY.
Losses occur when crops are stored-regardless of the storage
method Those losses are real--colorless, odorless and mvisible -
you can't see them, but they're there.
The air trapped within stored feed begins the fermentation process
-and fermentation continues until all the air is consumed. The less air
within the stored feed, the less loss.
Because bunker silos are not easily packed, losses in bunker silos
range from 27% to 45%. If the feed is valued at $3O per ton, every
1000 tons stored in a bunker would suffer losses from $B,lOO to
$13,500. Tower silo losses range from 3% to 8%, or $9OO to $2400
for every 1000 tons.
Those losses occur for every 1000 tons--every time feed is stored,
year after year Before investing in any storage method, consider
the total cosfs-mcludmg fermentation loss.
Compare the various methods of feed storage Contact the Crop
Storage Institute for your free copy of" Methods of Crop Storage" and
"Know the Facts."
Dr. William E. Fry, Depart
ment of Plant Pathology, Cor
nell University, told about 150
potato growers that the new
isolate could be more fit,
more virulent, more aggres
sive, survive longer, and
resist most major fungicides
in the long run.
covered in New York, Virginia,
Tennessee, South Carolina, and
Florida, according to the research
er. US-8 isolates have been discov
ered in New York, Maine, Pen
nsylvania, North Carolina, Georgi
a, Florida, Michigan, Illinois, Ore
gon. and Washington.
Because of the subsequent soft
rot because of blight infection,
many potatoes were culled and
dumped after harvest. These
dumping sites can easily store mat
ing types.
Withthe new A-7 and A-8 mat
ing types, reproduction is possible.
As a result, * ‘oospores” are gener
ated, which can “recombine”
traits and make the fungus more
durable. Oospores can survive on
clothes, equipment, soil, and other
places. They can even survive
freezing.
The two long-term problems
UP TO 45%
Crop Storage Institute
219 N. 4th St. P.0.80x 560
Lafayette, Indiana 46902-0560
Even Maine had problems
with late blight because of the
bad weather conditions last
year, according to Leigh Mor
row, extension crop special
ist, University of Maine.
with the mating types are the fact
that they can mutate and that the
oospores have “a good survival
structure.” said Fry. “They can
survive a lot of things.”
Fry examined some trials with
various types of fungicides. The
important thing for growers to
remember is that they must apply
fungicides early and often. Apply
ing a low dosage frequently rather
than a high dosage infrequently
works best in blight control,
according to Fry.
Also, growers need to commu
nicate with each other about the
spraying programs, so that both
can work together to ensure the
blight is under control. Potato
growers need to keep an eye out
what is happening around them
if a neighbor is growing tomatoes,
and the tomato plants aren’t being
treated for late blight, the risk of
outbreak in potatoles is intensified.
“There is no silver bullet,” said
Fry, “for dealing with late blight.’ ’
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Terry Bourgoln, director of
plant Industries, Maine
Department of Agriculture,
spoke about the importance
of making sure the fungus
does not overwinter In
storage.
Management will depend on a var
iety of factors, especially weather.
According to Fry, New York
extension believes late blight will
be a problem this year.
Conditions need to be humid,
warm, and wet for late blight to
occur. If the season proves hot and
dry, late blight shouldn’t be a fac
tor, according to growers.
Growers need to improve scout
ing, weather monitoring, and more
closely inspect the seed source for
signs of blight. Work is being con
ducted at several universities on
coming up with blight-resistant
cultivars, of which some work
proves promising.
At the Wednesday morning
annual meeting of the cooperative,
Roger Springer, general manager,
told those present to “communi
cate and ask a lot of questions. It’s
a serious situation that we all need
to come to grips with.”
Even Maine had problems with
Authorized
UPS Station
Dr. Donald Daum, Depart
ment of Ag Engineering,
Penn State, provided Infor
mation on “getting the whole
plant covered" with a spray
program.
late blight because of the bad
weather conditions last year,
according to Leigh Morrow,
extension crop specialist. Univer
sity of Maine. Particularly hard hit
was the east and northeast portions
of the state, in Aroostook County.
Where areas had twice the rainfall,
the problem was really serious,
according to Morrow. The drier
areas of the state were able to keep
late blight under control.
The total Maine potato cull crop
was 500,000 CWT, and piles were
covered and composted. What
growers learned through the exper
ience was the importance of con
trolling the inoculum “and pro
tecting foliage and that’s it,”
said Morrow.
He told the growers to check the
seedlots and “test your seed.
“I don’t think we can expect to
go to zero tolerance on blight," he
said.
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