Based on weather station reports from six locations in Florida strawberry growing areas, the information is available on the Internet at http://agroclimate.org/tools/strawberry. It uses sensors to measure the length of the most recent wetness period, either rainfall or dew, along with temperature.

Designed to be simple to use, when there is no danger of disease, the weather stations on the map are green. In moderate risk periods, they turn to yellow. When disease is most likely to develop, they’re red.

Graphs showing conditions for disease development over the past month are available as well. Growers can also sign up to get e-mail and text message alerts when conditions change to moderate and high. There is no fee to use the system.

“The idea is to help growerssave money by not spraying unless there’s a real possibility of the disease developing,” Peres says.

“The standard has been to spray once a week as a preventive spray because strawberries are a high-value crop and growers don’t want to risk it. Sometimes they might even spray twice a week.

“I want them to spray only when conditions are favorable for disease in order to help them reduce cost and pesticide use and also to help save the fungicides we do have.”

Results from trials testing the disease modeling over four seasons showed that growers could reduce fungicide use by half, on average, when following the system. Peres determined the environmental variables for disease development and Clyde Fraisse, a University of Florida agricultural engineer, designed the Web program.

“The key was to develop the disease model,” Peres says. “Clyde is the computer expert. That is not my expertise.

“For Botrytis to develop,there needs to be above 12 hours of leaf wetness. Fourteen hours is ideal. About 16 to 20 degrees Celsius is the temperature Botrytis likes best.

“Anthracnose needs warmer temperatures to really develop, up in the 20 to 25 degrees Celsius range. That means a field can have one disease, but not the other.”

The system also recommends products to apply, based on specific climatic conditions. “If the strawberries have blooms, it recommends certain products to protect the flowers against Botrytis. If there are no blooms, it recommends different products,” she says.

Whether conditions are prime for Botrytis and anthracnose to develop next season is anybody’s guess.

“This season when everything was right for it, boom, we had one week of a big Botrytis outbreak. Growers were getting a lot of rejections of strawberries from markets up north because the gray mold developed on the way,” Peres says.

“Growers didn’t understand what was happening. It was clearly fungicide resistance. It now puts us in a whole different situation.”