2018 Crop Protection Guide for Tree Fruits in Washington

General Recommendations

Friday, September 21, 2018

Alternate Middle Spraying

Alternate middle spraying is a technique that applies full spray coverage to the outside rows and row ends, but skips every other row middle in the interior of the orchard. The operator applies the next cover for the pest or disease, if necessary, in the previously skipped row middle.

Alternate row spraying may be used when trees are small or very open to spray penetration, and the target pest or disease does not require full coverage for acceptable control.

At times, this application method is beneficial:
1.     When the time it takes to apply the spray is more important than excellent coverage. For example, after an apple scab or fire blight infection, the degree of control depends on rapid treatment and full coverage. Skipping alternate rows will lead to a reduced degree of coverage, but much more rapid treatment of the orchard. In this case, spray the skipped middles as soon as possible after completing the alternate middle application.
2.     When overtree irrigation, heavy rain, or cooling frequently reduces protective spray residues. The operator may apply the first of a series of spray covers at a full recommended rate to the entire orchard. Make subsequent applications to alternate row middles at a more frequent interval than usual, and at the normal rate per 100 gallons of spray mixture. Do not spray at an interval less than the product label allows.

Alternate row middle spraying is not recommended if the pest requires complete coverage for acceptable control. Complete coverage greatly improves control of pests and disesases such as codling moth, leafrollers, San Jose scale, mites, pear psylla, mealybugs, mildew, apple scab (eradicant sprays), and fire blight.

Tree Fruit Research & Extension Center, 1100 N Western Ave, Washington State University, Wenatchee WA 98801, 509-663-8181, Contact Us