The distribution of scab in pecan trees in relation to fruit weight

Authors: Bock, Clive; Hotchkiss, Michael - Mike; Wood, Bruce

Submitted to: Pecan Grower
Publication Type: Trade Journal
Publication Acceptance Date: 11/13/2015
Publication Date: 12/1/2015
Citation: Bock, C.H., Hotchkiss, M.W., Wood, B.W. 2105. The distribution of scab in pecan trees in relation to fruit weight. Pecan Grower. 26:24-39.

Interpretive Summary: Pecan scab, caused by Fusicladium effusum is the most destructive disease of pecan in Georgia and elsewhere in the southeastern US. We describe 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. This is discussed in the context of disease management.

Technical Abstract: Pecan scab, caused by Fusicladium effusum is the most destructive disease of pecan in Georgia and elsewhere in the southeastern US. We describe 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. This is discussed in the context of disease management.