Web-based forecasts improve strawberry fungicide timing

08/01/2011 05:40:00 PM
Vicky Boyd

Nobody likes rotten strawberries. That’s why growers tend to apply fungicides to their fields on regular schedules The problem with spraying antifungal agents when the calendar — or your gut feeling — tells you to is that you can end up applying more fungicide than you need to.

A related problem is that you might unknowingly apply fungicides to which diseases have become resistant. By the time you figure that out, you may have wasted hundreds of dollars on fungicides, and Botrytis gray mold or anthracnose fruit rot may have gained ground.

The good news is that researchers have developed what seem to be promising solutions to each of these dilemmas.

With the help of a $2.9 million U.S. Department of Agriculture specialty crop initiative grant, Natalia Peres, associate plant pathology professor at the University of Florida’s Institute of Food and Agricultural Sciences in Balm, has developed a model that alerts you when it’s time to spray.

The computerized system analyzes leaf wetness in conjunction with the temperature to come up with a probability of Botrytis gray mold or anthracnose fruit rot developing during a certain timeframe.

And at Clemson University in South Carolina, Guido Schnabel, professor and Extension fruit pathologist, has developed a kit that helps you quickly determine whether a particular kind of rot is resistant to the fungicide you plan to spray.

Cost savings

Reducing fungicide applications can be a boon to growers. Peres estimates that fungicide alone costs about $50 per acre, not counting labor, time and equipment costs.

She looks for two main factors when determining whether to issue a spray alert—leaf wetness and the temperature during that wetness period. In general, if the temperature tops 65 degrees and the leaves are damp, it’s time to spray.

“If it reaches the threshold we set up for each disease, we send an alert,” she says. The alert can be in the form of an e-mail or text message for which growers can sign up or a Web announcement.

Of course, Peres’ calculations are much more scientific and also take into account other factors, such as the particular host, pathogen and environment as well as fungicide performance during past seasons.

Peres is pleased with the results so far. Over the past two years, those who followed the program and sprayed only when conditions were optimal for disease have been able to reduce pesticide use by up to 50 percent, she says.

The project also is being evaluated in North Carolina, South Carolina, Ohio and Iowa. If it is successful there, systems will be developed for those states.

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