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IPM 25th2005 Annual Report

UC Statewide IPM Program

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 higher yields, but they increased the risk of cold weather damage.

The 5-day 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 planted 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 summaries.

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, and unfavorable.

"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.

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