Observations in Treating Non-Bearing Pecans with Phosphite
Horticulture & Turfgrass
Andrew Sawyer
Area Extension Agent
University of Georgia
Statesboro
Abstract
Phosphites, a reduced form of phosphate, are used as a fungicide and are very effective at controlling pecan leaf scab. Highly scab susceptible varieties require a season long fungicide spray program to reduce the effects of pecan scab (Fusicladium effusum). With significant increases in pecan planting in Georgia, no research has shown when to begin a fungicide spray program for non-bearing trees or whether pecans should benefit. Additionally, phosphite has shown both positive and negative response in different crops but not pecan. This three-year study was conducted in Laurens County, Georgia to determine if phosphite use translated into a disease or horticultural benefit for pecan trees. This test was conducted on 3-year-old ‘Caddo’, a medium scab susceptible variety in Laurens County, GA and 4-year-old ‘Byrd’, a high scab susceptible variety in Bleckley County, GA. Four treatments of differing rates and intervals of K-Phite 7LP were replicated four times. Tree growth, scab control and leaf nutrient samples were compared among treatments. Leaf analysis showed no inteference with nutrient uptake by phosphite. Disease ratings presented a precise date to which fungicide sprays should begin based on scab susceptibality pecan cultivars. Lastly, leaf tissue samples showed translocation of phosphite in pecan trees.
Authors: Andrew Sawyer
-
Andrew Sawyer Area Extension Agent, UGA Extension, Georgia, 30460