System helps forecast strawberry diseases

08/06/2013 10:39:00 AM
Renee Stern

"It's more important for growers to spray only when they need to," she says.

Improved disease control wasn't her goal. "I don't know if we could get that with the tools available," she says.

Instead, Peres aims to optimize fungicide use. Growers using the system have reduced their sprays by a third to a half "without compromising disease control."

"You have to have the courage to believe the model," Calfee says. That's not an easy proposition for new users, especially when faced with what looks like a serious botrytis event in the making—but trust comes with experience.

Conduct a small trial first

Calfee hesitated at first. "It's the kind of thing you don't want to bet the whole farm on," he says. Like Grooms, he experimented with small trials and added acreage each year as his confidence in its recommendations grew.

Last year he expanded fungicide management with the tool to 83 acres. "It did so well I put all of our strawberry acreage on it," he says.

Grooms recommends new users focus it on only part of their farm "and see it through" for a full season rather than a single spray cycle.

Once the season ends, compare the number of fungicide applications on that section to the rest of your strawberry fields, the amount of management time spent on disease control, and any differences in fruit quality and losses, he says.

The results should simplify the decision whether to commit fully to the advisory system, Grooms says.

Calfee also has done comparison tests, following the model's recommendations not to spray on some sections and pitting them against other sections following the old calendar-based schedule.

"The results bear out" in favor of the model, he says.

Growers may need to customize model

But growers may need to modify recommendations with their own site knowledge and experience.

"It's an accurate model," Calfee says. "But like any tool you have, you've got to use it when it makes sense."

Scheduled irrigation, for example, could increase disease risk—but fall outside the model's considered factors, he says.

At the same time, experience with the model also can filter into growers' considerations.

"I've been working with it long enough to have a sense of when conditions will trigger an alert,"

Grooms says.

The model measures the duration of leaf wetness, either dew at night or periods of rain, and the temperature during those wet periods, Peres says. Botrytis and anthracnose fungi need both moisture and temperature to hit threshold levels before they develop and colonize fruit.

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