Fruit size of peaches is an important quality factor that can be optimized by adjusting the number of fruit on the tree by hand thinning 40 - 60 days after full bloom (dafb). Hand thinning is labor intensive and therefore the development of other strategies to reduce production cost is warranted. Since ethylene plays a key role in peach fruitlet abscission, it is hypothesized that foliar applications of ethephon will induce fruit abscission and increase fruit size. Ethephon (0 to 400 mg·L –1 ) was applied to “Redhaven” peach trees 45 - 50 days after full bloom in 2005 and 2007 to determine the efficacy and concentration required to induce fruit abscission. Abscission was linearly related to ethephon concentration and as a result reduced fruit set by 70% to 100 %. These data indicate that ethephon in the range of 100 - 200 mg·L –1 can be used to induce adequate levels of fruit abscission of ‘Redhaven’ peaches without inducing trunk or limb gummosis.
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