204 POTENTIAL OF BLOWN AIR AS A THIGMIC STRESS FOR TEMPORARY NONCHEMICAL PRIMOCANE SUPPRESSION OF RED RASPBERRY

The red raspberry industry of the Pacific Northwest depends upon chemical primocane suppression to temporarily reduce competing vegetation during fruit development. This practice increases yield and harvest efficiency, but can reduce cane vigor, number and diameter over time. Few chemicals are available for this purpose and thus the potential of nonchemical alternatives is being explored. The purpose of this project was to evaluate the potential of blown air as a thigmic stress to temporarily suppress primocane growth. Blown air treatments were applied once (12 PM) or twice (12\4pm) per day, five days per week using a portable leaf blower generating winds of 273 km per hr. Treatments also included several rates of three experimental herbicides and an untreated control. All treatments were applied when primocanes were 10-15 cm in length and blown air treatments continued through fruit development. Primocane development was monitored over the course of the season. Blown air reduced primocane length by 15-30% prior to harvest giving control equivalent to current chemical methods. Blown air increased cane diameter but reduced yield by reducing fruit numbers. Reductions in fruit numbers are likely due to flowering\fruiting points removed by blown air.