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ARS Home » Southeast Area » Byron, Georgia » Fruit and Tree Nut Research » Research » Publications at this Location » Publication #327556

Research Project: Mitigating Alternate Bearing of Pecan

Location: Fruit and Tree Nut Research

Title: Fruit and nut weight in pecan trees canopies in relation to the severity of pecan scab at different heights

Author
item Bock, Clive
item Hotchkiss, Michael - Mike
item Wood, Bruce

Submitted to: Forest Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/22/2016
Publication Date: 2/7/2017
Citation: Bock, C.H., Hotchkiss, M.W., Wood, B.W. 2017. Fruit and nut weight in pecan trees canopies in relation to the severity of pecan scab at different heights. Forest Pathology. 47:e12331.

Interpretive Summary: Pecan scab, caused by Fusicladium effusum is the most destructive disease of pecan in the southeastern US. This study addressed the distribution of scab and measures of yield in relation to sample height in tall trees. Control trees had significantly more severe disease on fruit lower in the canopy, while fungicide-treated trees either had similar disease severity at all heights, or slightly more disease in the upper canopy. Where relationships existed, on control trees yield and sample height invariably had a positive linear relationship. On fungicide-treated trees, yield most often had a negative linear relationship with sample height. In control and treated trees there was invariably a negative linear relationship between disease on fruit and measures of yield. Gradients in fungicide coverage and scab severity have impacts on measures of yield that can have ramifications on yield and quality of nuts for the tree as a whole. Understanding the distribution of disease in pecan canopies provides a basis for developing tree management strategies and fungicide application methods to uniformly minimize disease.

Technical Abstract: Fusicladium effusum is the cause of pecan scab, the most destructive disease of pecan in the southeastern US. This study addressed the distribution of scab and measures of yield in relation to sample height in tall trees (14 to 16 m tall) in three experiments in 2010 and 2011 with trees receiving fungicide using an airblast sprayer or non-treated as controls. Samples for disease assessment and measures of yield were taken at 0-5.0, 5.0+-7.5, 7.5+-10.0, 10.0+-12.5 and 12.5+-15.0 m. A general linear mixed model analysis showed main effects of sample height, fungicide treatment, and sample height × fungicide treatment interactions in all three experiments for disease and yield (<0.0001<P<1.0). Control trees had significantly more severe disease on fruit lower in the canopy, while fungicide-treated trees either had similar disease severity at all heights, or slightly more disease in the upper canopy. Where relationships existed, on control trees yield and sample height invariably had a positive linear relationship (0.85< R2<0.94). On fungicide-treated trees, yield most often had a negative linear relationship with sample height (0.69< R2<0.89). In control and treated trees there was invariably a negative linear relationship between disease on fruit and measures of yield (0.66< R2<0.94). Gradients in fungicide coverage and scab severity have impacts on measures of yield that can have ramifications on yield and quality of nuts for the tree as a whole. Understanding the distribution of disease in pecan canopies provides a basis for developing tree management strategies and fungicide application methods to uniformly minimize disease.