QUINCY — Researchers on at least one project in this agricultural community are seeing red. And blue. And an off-white tint called pearl.
Washington State University tree fruit scientists have gotten the green light to test the effects of colored orchard netting stretched over 12 acres of Honeycrisp apples west of Quincy.
Findings are still preliminary, but one year and two harvests into the 3-year study have shown the colored netting — installed in three hues — has measurable effects on soil, trees and fruit that could benefit an apple grower’s bottom line.
Among other results, testing has shown that colored nets “affect the quality of light, scattering it, diffusing it,” researcher Stefano Musacchi told a gathering of around 70 growers and fruit industry representatives Wednesday at an WSU-sponsored orchard netting field day. “And that (diffused light) could be effective in manipulating tree and fruit growth.”
Many growers in the state have used white netting for years to protect delicate fruit from hail and extreme sun, said WSU researcher Lee Kalcsits, who with Musacchi led Wednesday’s tours under the colored canopies. “They began seeing other (growing and production) benefits from using the nets, but those benefits were all anecdotal,” he said. “Now we’re testing.”
In 2015, researchers installed the colored netting on a McDougall & Sons plot of Honeycrisp, a low-vigor apple variety that requires attention and tweaking to produce the high-quality fruit that’s so popular with consumers. Sensors monitor air and soil temperatures, wind speed and light intensity.
The entire netting structure cost around $18,000 per acre, said Kalcsits, “but this is the Cadillac of orchard netting — poles, supports, wiring, and the netting itself are all first rate. And labor is included in that figure.” He said less expensive netting structures are available.
Kalcsits said the WSU research team has focused on three main objectives: how the overhead netting affects the orchard environment (soil, temperature, moisture, wind), how trees respond to changes in environment (growth and photosynthesis) and how fruit reacts (size, color, maturity) to those environmental changes.
A year of testing indicates that colored nets “fine-tune” the overall effects of netting, increasing some aspects of production and reducing others, said Kalcsits.
Some initial findings:
- Overhead canopies reduce sunlight by 20 to 25 percent but increase the amount of scattered or diffused light between the netting and the ground. Diffused light can help improve fruit color and maturity on lower branches.
- Direct sunlight — often strong and harsh — can cause a tree to “shut down” its photosynthesis and fruit-nurturing processes. Trees outside nets typically reduce photosynthesis on hot days around 11 a.m. in order to conserve water. Photosynthesis in trees under nets has been measured to continue longer each day.
- Under nets, tree and fruit growth has shown increases of 16 to 18 percent.
- Testing under the nets shows little change in air temperature or humidity. The nets don’t affect the air, but instead reduce the sunlight — energy — reaching the trees and fruit.
- Outside the nets, ground surface temperature on a very hot day can easily reach 90 degrees or more. High soil temperatures can put stress on root growth. Under the nets, surface temp can be reduced by 5 to 7 degrees.
- Outside the nets, sunburn on fruit can reach 25 percent in some orchards. Under the nets, sunburn measures from 5 to 8 percent.
- More specifically, trees under the pearl (off-white) netting have shown robust growth in lateral branches, reduced light stress and increased photosynthesis. Under blue nets, leaves seem to grow slightly thicker and tree vigor improves. Under red nets, fruit color seems to improve.
- Whether psychological or physical, one effect from colored netting is that fruit pickers say conditions under blue nets feel cooler than under red nets. Red looks hotter and therefore seems so, researchers surmised.
- Bird damage to fruit is reduced under netting. “For some reason,” said Kalcsits, “birds don’t like to be under a canopy.”