UC IPM Makes It Happen
UC IPM offers accurate forecasting tool for cotton growers
Before the advent of a weather forecasting tool, cotton growers planted
their crops based on soil moisture and soil temperatures.
If farmers delayed planting, hoping for better weather, they reduced
the time for plant growth. If they planted too early, they might get
but they increased the risk of cold weather damage.
degree-day forecast for cotton planting was developed during
the mid-1980s to provide an indication of the risk to germinating cottons
seeds based on forecasted air temperatures. The UC Statewide IPM Program
offers this tool that has proven to be a great benefit for growers.
"The cotton forecasting tool has become the guide to which everyone
turns come planting time," says Earl Williams, president
and CEO of California Cotton Growers and Ginners Association. "Of
course there are exceptions, but I would say that there is not one seed
without a look being
given to the tool, at least. Needless to say, I'm sold and I believe
the industry is, as well. It's given the growers something to base these
important decisions on, rather than the old way that was soil temperature
is close, calendar says it's time, and my neighbor has started so it
must be time. With the cost of seed today, in addition to all the related
costs and time, growers must be more accurate with these decisions. This
tool has made the accuracy of such decisions much better, and I believe
has saved an enormous amount of money for the industry."
In 2000, a survey of cotton growers found that 87 percent used the
degree-day forecast in their cotton planting decisions. In a study evaluating
the accuracy and reliability of the planting forecasts for Bakersfield
and Fresno, compared to observed air temperature data for 1998 through
2002, the tool gave an accurate forecast 75 percent of the time. The
survey showed that in nine percent of the inaccurate cases, the forecast
underestimated the observed category and actual air temperatures, and
resulting planting conditions were more favorable than predicted.
The most serious error occurred when the predicted category was in
the marginal or adequate categories so farmers might have decided to
plant, but then the observed category was unfavorable. This error occurred
in only seven percent of the cases during this five-year period.
For many years, the National Weather
Service (NWS) calculated the cotton
5-day degree-day forecast for Bakersfield and Fresno. The information
was broadcast over the National Oceanic and Atmospheric Administration
Weather Radio throughout the San Joaquin Valley during the cotton-planting
season. When the NWS stopped providing this forecast, UC cotton advisors
and specialists asked the UC Statewide IPM Program to calculate the degree-day
In 1997, the UC IPM information systems group began posting the forecasts
on the UC IPM Web site each day during cotton-planting season. The observed
lows for the morning (as reported for Fresno, Bakersfield and Chico)
are used as the minimum temperatures for the first day of the period.
The page is updated each day from about March 10 through April 30.
The planting forecast categorizes the predicted heat units (a unit
combining temperature and time used to monitor growth and development
of organisms) into degree-day groups—ideal, adequate, marginal,
"When the forecast comes in as marginal or unfavorable, the tractors
stop," says UC IPM Advisor Pete Goodell, who works closely with cotton
growers in the San Joaquin Valley. "Cotton growers really use this as
a major decision tool, and it predicts very well whether you will get
a good stand."
More information about this
beneficial tool can be found on the UC IPM Web site. The cotton planting forecasts
for 2006 will be available after March 10.