By DAN WHEAT

Capital Press

PROSSER, Wash. -- Researchers are studying cold hardiness of several apple and cherry varieties to help growers know better when to protect against frost.

A three-year study began last February but there may be some results to help growers a year from now, said Melba Salazar-Gutierrez, a Washington State University research associate involved in the work at the WSU Irrigated Agriculture Research and Extension Center at Prosser.

When it comes to running wind machines, heaters and irrigation for frost protection, growers rely on data developed 30 to 40 years ago on a limited number of varieties. Techniques were effective only for early stages of bud development.

The $255,000 study seeks to update and expand the data to give growers more precision in knowing when to turn to frost protection at various stages of growth, including later bud and bloom growth.

The work is led by Gerrit Hoogenboom, AgWeatherNet director, and Salazar-Gutierrez. It is funded by the Washington Tree Fruit Research Commission.

Resistance to freezing depends on bud development. Varying susceptibility makes it difficult for growers to know when to initiate frost prevention measures, Salazar-Gutierrez said.

Flower buds are increasingly vulnerable as they develop, and the effects of freezing is not uniform in dormant buds, she said. Damage may be more extensive at full bloom, depending on the severity of a freeze.

The work involves an automated freezer sampler, called the vending machine, created by IAREC staff member John Ferguson to determine cold hardiness of grapes. The machine exposes buds to different cold temperatures and duration.

Salazar-Gutierrez is still analyzing tests of Red Delicious, Gala and Fuji apples from last spring as well as tests of Bing, Chelan and Sweetheart cherries.

Bud samples were collected from the WSU Roza Research Farm and from C&M Orchards near Prosser. Salazar-Gutierrez said she would like to find one more orchard to collect samples from next spring.

She plans to analyze samples for two more seasons and wants to study how apple and cherry buds fare in fall and winter as they enter dormancy.

She will develop a model with a range of early spring temperatures that buds at all stages of development will tolerate.

"The overall outcome will be updated hardiness charts for apples and cherries that include critical temperatures for each of the different stages of spring bud development," Salazar-Gutierrez said. "This will allow for better planning to improve fruit quality, enhance yield and ultimately increase net returns."