When walnut flowers senesce prematurely in an orchard affected by pistillate flower abscission (PFA), and thus fail to pollinate and set, a grower’s productivity and potential revenue are adversely affected.
By temporarily blocking the production of the naturally occurring plant hormone ethylene during anthesis, ReTain® Plant Growth Regulator from Valent U.S.A. Corporation extends a flower’s life and increases the window for its pollination.
By applying ReTain multiple times during that critical period, a grower can protect a larger number of flowers—those that bloom early and those that bloom later—and achieve both increased nut set and profit opportunity.
The best time for growers to apply ReTain to walnuts is in late March or early April—or between 5%-30% and then again at 50%-60% pistillate bloom—waiting 2-4 days between applications. If it’s warm during this time, growers should generally apply every two days. If the weather is cooler, you can apply at four-day intervals.
While Serrs have responded very well to multiple ReTain applications in past years, research conducted in 2012 and 2013 showed excellent results in the Tulare and Chandler cultivars as well.
Multiple applications of ReTain at the full rate delivered the most profitable yield in Serrs, Tulares and Chandlers, as opposed to just one application or no applications of ReTain. While PFA-affected Chandler and Hartley cultivars responded more moderately than Serrs and Tulares, it is still profitable at today’s walnut prices to apply ReTain to those cultivars.
Enhancement of nut set is dependent upon flower density and the level of PFA in a given orchard. Flower density is affected by several factors, including the number of chilling hours that season, the health of the orchard, quality of fruiting wood, nutrition and maintenance.
To learn more about ReTain and the rest of Valent’s portfolio of tree nut products, visit valent.com.