Published on 02/05/04

Doppler radar helps fight peanut diseases

By Brad Haire
University of Georgia

Peanut farmers can use a common weather radar to better protect their crop from fungal diseases this year. And it's just a click away.

Doppler radar is a weather tool commonly used by TV news meteorologists to show and predict weather. But it can also be a high-tech rain gauge farmers can use to measure rain in and around their fields, said Bob Kemerait, a plant pathologist with the University of Georgia Extension Service.

Timely fungicide

Knowing how much rain falls in a field is important in keeping fungal diseases like leaf spot, white mold and limb rot under control, Kemerait said.

Farmers spray fungicides to fight these diseases.

But in the past, the times when farmers have sprayed hasn't been a precise practice. Most peanut farmers stick to a strict calendar schedule. They spray fungicides about 30 days after planting and then once every two weeks until harvest. This can add up to about seven sprays in one growing season (mostly from May to October).

It costs about $7 per acre to spray fungicides on peanuts. That's not counting tractor fuel or labor. If a farmer has 500 acres of peanuts, he could easily spend $24,500 in one year on fungicides alone.

And sticking with the calendar schedule means a farmer sprays regardless of the weather. A grower could spray too late to effectively control a fungal-disease outbreak or spray when he really doesn't have to.

Fungal diseases like rainy conditions. In fact, scientists know if it rains more than one-tenth of an inch in a 24-hour period, conditions are prime for fungal diseases to start assaulting peanuts.

"But most farmers don't have the time to go to every field they have and consistently check rain gauges for that one-tenth-of- an-inch rain trigger," Kemerait said. It's easier to keep up with the calendar schedule.

Rain gauge

This is where the Doppler radar can help. Now, a farmer doesn't have to go from field to field to check rain gauges. He can do it all from a computer at home, Kemerait said.

Farmers can get free Doppler data of their fields from AWIS Weather Services, he said. A farmer can register his fields at He will need the global positioning satellite coordinates of his fields to do this.

Kemerait and other UGA scientists in Tifton, Ga., have checked to see how accurate the Doppler radar can indicate that one- tenth-of-an-inch trigger.

They registered 10 sites across Georgia for AWIS Doppler data. These sites were also monitored for actual, real-time weather conditions by UGA's Georgia Automated Environmental Monitoring Network.

The monitoring sites and the Doppler radar agreed more than 90 percent of the time in indicating rainfall of one-tenth of an inch or more, he said.

A farmer can take rainfall data, along with future rain predictions, and better plan a fungicide spray program, Kemerait said. He can spray or omit sprays as needed, he said, and stay ahead of fungal diseases.

There are advisory systems farmers can use to easily do this with the data. AU-Pnut is one system developed at Auburn University.

Even technology that's been around for a while, like Doppler radar, can increase the speed in which some farm work can be done and make it more efficient, Kemerait said. It can allow a farmer to better manage an entire region by simply logging onto a computer anywhere.

"Technology in agriculture will never totally replace the need to have someone on the ground at some time," he said. "But it provides tools to help take some of the legwork out of it."

Brad Haire is the former news editor with the University of Georgia College of Agricultural and Environmental Sciences.