Save Your Apples: More information on new sunburn protection products

From the July 2007 article "Save Your Apples: New products promise to protect crops from weather while saving resources."

The fruit surface temperature sensor developed by Larry Schrader, a plant physiologist and horticulturist with the Washington State University Tree Fruit Research and Extension Center, can help reduce sunburn on apples when used with evaporative cooling. And if growers are interested, it's about to become even more high-tech.
The sensor, available to growers in 2003, was initially developed as a stand-alone unit that growers could use in their orchards to measure fruit surface temperature in the mid-afternoon, from 1:30 p.m. to 4:30 p.m. when temperatures reach their highest points, according to Schrader. The sensor connects to a transmitter with a liquid crystal display and a receiver that transmits the temperature up to 100 feet from the sensor. Many growers mounted the sensor outside their orchards and kept the display in their vehicles so they could drive up to the sensor, read the temperature, and then go turn on their irrigation pumps for evaporative cooling.

Today, Schrader wants to measure interest from growers in a more sophisticated version of the sensor that could transmit fruit surface temperature to the temperature controller and automatically turn on the irrigation pump when temperatures reach the danger zone.

"For example, the grower could set his evaporative cooling to come on when the temperature of his fruit reaches 104 degrees F and then turn it off when the temperature comes down to 95 degrees F," Schrader says. "Sunburn varies by variety but it typically does not occur until the fruit surface temperature reaches about 115 degrees F. I like to keep a margin of safety."

Some growers already use the sensor in a high-tech fashion, Schrader says. "I was standing in an orchard with a grower one day and the guy's cell phone came on and said, 'It is time to activate your EC (evaporative cooling),'" Schrader says. "We're working to further improve the product because a lot of growers would like to have it call their cell phone or dial up their laptop in their pickup. They don't want to have to run out to the orchard every couple of hours to check the temperature."

There can be other benefits to a more automated version of the sensor, as well, Schrader says. Together with Raynox, a wax emulsion product Schrader developed to apply to fruit and protect it from harmful ultraviolet rays that cause sunburn, trials have shown the fruit surface temperature sensor can reduce sunburn by 95%.

"My research has shown that a combination of Raynox and evaporation cooling is really the best practice," Schrader says. "The advantage of using the sensor with evaporation cooling is that not only does it reduce sunburn, but it also reduces water use. One grower told me he cut his water usage to one-third of what he was using previously."
For more information on the fruit surface temperature sensor and to express interest in a high-tech version, contact Larry Schrader, schrader@wsu.edu.