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ARS Home » Southeast Area » Byron, Georgia » Fruit and Tree Nut Research » Research » Research Project #435669

Research Project: Mitigating Alternate Bearing of Pecan - Bridge Project

Location: Fruit and Tree Nut Research

Project Number: 6042-21220-013-00-D
Project Type: In-House Appropriated

Start Date: Oct 23, 2018
End Date: Dec 31, 2019

Objective:
1. Mitigation of alternate bearing by individual trees, and affiliated reproductive subunits, by improving canopy health and longevity. 1.A. Determine if canopy exposure to ammonium and/or cytokinin can increase flowering, fruit-set, and improve health and longevity of pecan tree canopies. 1.B. Determine if increasing root exposure to ammonium by way of soil fertilization alone or in conjunction with canopy applied urea and flowering bioregulators can increase flowering, fruit-set, and improve canopy health and longevity. 2. Develop improved integrated management of pecan foliar and fruit diseases, with emphasis on pecan scab. 2.A. Determine ways to provide better control of scab and other pathogens in pecan trees based on an understanding of disease progress, tree stress and canopy health. 2.B. Develop an improved basis for managing scab resistance using a knowledge and understanding of the characteristics of the genetic diversity and population biology of the scab pathogen.

Approach:
This research aims to provide pecan farmers improved and sustainable crop-load and disease management practices enabling mitigation of alternate (AB) bearing by pecan orchards. The goal of this research project is to provide U.S pecan (Carya illinoinensis) farmers with horticultural and disease management tools and strategies that enable them to mitigate alternate bearing (AB). The industry considers AB to be its most important biological problem. AB is an economically harmful, typically biennial, trait that causes excessive year-to-year fluctuation in nut yield and kernel quality. Many biotic and abiotic factors, and the stresses caused by reproduction, interact with innate reproductive physiology to either induce or increase the amplitude of this cyclical pattern. There are many important knowledge gaps pertaining to the biology and management of AB. This project targets whether fruiting in ‘Off’ (low crop load) years can be increased by appropriate and timely use of cytokinin (CK) and/or ammonium (NH4+) in the previous ‘On’ year to enhance production of female (pistillate) flowers the following year. It also targets whether reducing previous ‘On’ (high crop load) year tree stress caused by fungal diseases, particularly pecan scab (Fusicladium effusum), but also other stressrelated pathogens, can increase subsequent ‘Off’ year flowering. A series of field and laboratory studies over the next five years will address these key knowledge gaps and develop greater understanding and horticultural tools and strategies required for mitigation of AB.