BB—Lancaster Farming, Saturday, February 9,1980
How Blitecast cuts sprays,
costs
SAN FRANCISCO, Ca. -
For years, most East Coast
potato growers have suc
cessfully controlled the
dreaded disease late blight,
by using 10 weekly sprays of
a controversial chemical. At
$3.65 and a pound-and-a-half
per acre, it seemed a small
cost to protect potatoes
against the fungus that had
caused the infamous Irish
famine.
However, in Pennsylvania
alone, potato farmers each
summer apply 375,000
pounds of fungicide, at a cost
of nearly $1.4 million.
In the early 19705, Penn
State researchers developed
a computerized pest
forecasting system, that
predicted peak damage
periods. Called Blitecast, the
system permitted potato
growers to cut the number of
sprays to five or six, and to
reduce their spraying costs
by almost half.
The technique worked
“incredibly well” for several
years. Participating far
mers saved a lot of money,
and hundreds of thousands of
pounds of chemicals were
not needlessly used.
Still, may potato farmers
continued to “play it safe,”
routinely spraying at least 10
tunes each growing season.
Why didn’t all Penn
sylvania potato farmers
choose to use Blitecast 9
That’s what Penn State
plant pathologist David R.
MacKenzie has been trying
to determine.
“The answer,” MacKenzie
told the annual meeting of
the American Association
for the Advancement of
Science, “seems to be that,
although we scientists can
develop such forecasting
methods, we can’t yet tell
farmers what the risks are.
“Quite often,” said
MacKenzie, a noted potato
researcher and pioneer in
computerized plant pest
forecasting, “we don’t un
derstand why particular
forecasting techniques work,
and thus can’t promise
they’ll work every time
“It’s thus possible that an
explosive pest problem, such
Yes liming pays it pays in extra bushels and tons of crops, in health
ier, more profitable livestock, in the increased worth of properly limed
land, and it pays in the satisfaction that comes from doing a better job
of farming
by 50 percent
as potato late blight disease,
could result from a
forecasting failure-and this
could spell disaster for a
particular grower.”
Essentially, MacKenzie
maintained, pest forecasting
methods must be far better
understood, if they are to be
truly valuable to any crop
production scheme.
In the 19705, he explained,
researchers devised
tremendously successful
complex formulate to
forecast peak pest periods
for several crops. But while,
for example, it’s thus
possible to calculate that a
certain combination of
weather factors is likely to
lead to large pest build-ups
and hence to crop losses,
scientists don’t understand
the underlying assumptions
that make the system work.
“More importantly,”
MacKenzie adds, “we don’t
understand how best to
deliver such forecasting
information to fanners, in a
system they’ll accept. This is
true for potatoes, for which
the prediction system is
most advanced, or for such
other crops as apples and
alfalfa.”
Penn State researchers,
including computer scien
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tists and electrical
engineers, have developed
several “delivery”
MacKenzie said they are
ready to test these systems
on farmers, to help deter
mine how to best help far
mers with pest management
decisions.
To determine whether it
pays to spray-whether a
particular insect or disease
is about to do more damage
per acre than the cost of
spraymg-a grower can use a
computer, a programmable
pocket calculator, an
economic injury level graph,
or can call on a county agent
for help.
AH of these Blitecast
systems represent different
ways of interpreting the
previous week’s weather
information. To make a
forecast, a farmer monitors
his field’s temperature,
humidity, rainfall and other
factors.
Under the original
Blitecast system, factors
phoned their findings to the
University, where a giant
computer analyzed the
probabilities, and predicted
whether spraying was
needed.
To reduce the growing cost
burden to Penn State, Dr.
MacKenzie and five un
dergraduate students
developed a mini-computer,
called a ‘ ‘ Bhtecaster. ’ ’
Available since 1977 for
$llOO, the device
automatically monitors field
conditions. To determine
whether to spray, a farmer
only needs push a button.
“Though the Bhtecaster
has performed very well,
and now can be used for both
late blight and green peach
aphid,” MacKenzie said,
“only a few Pennsylvania
potato farmers have bought
one WV'- c glower could
recoup the machine’s cost in
one or two seasons and
thereafter save a lot of tune
and money, most farmers
seem unwilling to try. ”
Given pest forecasting
systems’ tremendous suc
cess and potential, he con
tinued, it’s important to
learn more about both the
systems and which ones
growers will accept.
Seeking these answers,
MacKenzie has begun
analyzing vast computer
stored weather records, and
corresponding incidences of
late blight. He’s particularly
interested in understanding
the relationship between the
past weeks’ weather and the
need to protect a crop the
following week-a major
assumption of Bhtecast.
Ultimately, he hopes to
learn not only how Bhtecast
works, but whether there’s a
better way of protecting
crops-a way most farmers
will accept.
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