By STEVE CASTAGNOLI
OSU Extension horticulturist
March 27, 2008

Recent information from the Columbia Gorge Fruit Growers (formerly Hood River Grower-Shipper Association) indicates that their Backyard Tree Program is putting a significant dent in the number of unmanaged fruit trees in the Hood River Valley.

The program promotes voluntary removal of unwanted fruit trees, as well as improved control of pests on remaining trees. The short term goal of the program is to eliminate the spread of pests such as codling moth from unmanaged trees to commercial orchards. The goal is to reduce the use of pesticides in local orchards.

The impact of unmanaged trees has become more significant in recent years because many Hood River orchards are using an innovative approach, known as pheromone confusion or mating disruption, as the foundation of their moth control program.

Mating disruption is a non-chemical control and is an example of “softer” pest management programs that use more selective, lower risk pesticides. Unmanaged pear, apple and even crabapple trees can serve as reservoirs of mated female codling moths that fly into an orchard and lay eggs on fruit. If this occurs in a mating disruption orchard where the fruit is not protected with a conventional insecticide, the efforts of the grower to employ an environmentally friendly method of pest management are ruined.

Since the Backyard Tree Program got underway in 2004, about one-third of the 500-plus households with pear, apple or crabapple trees have elected to remove those trees. An additional 18 percent of these households have done a satisfactory job of controlling pests on the trees they opted to keep. When these two groups are considered together, just over half of the potentially offending trees have either been removed or managed — a very encouraging result.

The Backyard Tree Program provides an incentive for those voluntarily removing pear, apple, and crabapple trees. They are providing coupons redeemable at Gorge Nursery and Good News Gardening towards the purchase of non-fruit bearing plants and participating Fruit Loop Members for fruit. To take advantage of this program, contact the Fruit Growers at 387-4769.

Most Hood River Valley fruit growers have begun applying pre-bloom sprays targeting pests that overwinter on the tree with low risk pesticides such as sulfur and horticultural mineral oil. If applied at this time of year, these cause minimal disruption of beneficial insects that provide biological control.

These early season sprays mark the beginning of a commitment to a season-long, integrated program aimed at preventing pest damage. The high level of commitment required to grow commercially acceptable fruit may not be apparent to hobby or novice fruit growers. Home fruit growers may neglect to control insect pests and diseases on backyard trees with few apparent consequences. As noted above, not controlling pests on home fruit trees may have serious consequences; however, because they often serve as sources of pest infestation to commercial orchards.

Pre-bloom sprays are important for home fruit growers also, but the most important sprays for home apple, pear and cherry trees don’t start until mid- to late-May in the lower Hood River Valley. These later sprays target codling moth, cherry fruit fly and apple maggot. These three pests are of special concern to fruit growers in the Hood River area.

Not only do these pests cause direct damage to fruit, each is a quarantined pest in some export destinations. If pests are not controlled, the county may require destruction of the crop and/or trees at the owner’s expense. Because of relatively high pest pressure in the Hood River area, non-chemical methods of controlling the key pests on home fruit trees generally provide inadequate results. Because these insects are all direct pests of fruit, annual removal of all fruit is one option. This must be done early in the season to prevent pest infestation and may be difficult to do on large trees or on trees with many small fruits.

The life cycle of most pests is dependent on weather conditions, which affect the time of pest emergence in the spring and development through the rest of the season. The effectiveness of pesticide applications is highly dependent on application timing. For specific information on current season pest emergence and determining when to initiate pesticide applications, contact your local OSU Extension Service. In Hood River County, call 386-3343.

This time of year, many people are planting new landscape trees and shrubs. Growing fruit trees in your yard may result in unintended consequences for nearby commercial growers. If you are planting new trees, think twice before choosing fruit trees such as pear, apple, and cherry or their fruiting ornamental relatives such as crabapple or hawthorn.

If you want to grow fruits but do not want to spray, consider growing fruits such as caneberries, strawberries and blueberries that will not impact surrounding orchards.

Several publications are available from the OSU Extension Service Office in Hood River and on the Web (http://eesc.orst.edu/).