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ARS Home » Southeast Area » Byron, Georgia » Fruit and Tree Nut Research » Research » Publications at this Location » Publication #286586
Title: The effect of height on severity of pecan scab in non-treated mature pecan trees

Author
item Bock, Clive
item Wood, Bruce
item Cottrell, Ted

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/12/2012
Publication Date: 7/2/2012
Citation: Bock, C.H., Wood, B.W., Cottrell, T.E. 2012. The effect of height on severity of pecan scab in non-treated mature pecan trees. Phytopathology. 102:S4.13.

Interpretive Summary: Pecan scab (Fusicladium effusum) is a destructive disease of pecan. There is concern that disease in the upper canopy of tall trees is difficult to control using ground-based sprayers. To establish a basic understanding of the distribution of scab in a non-treated pecan canopy, the vertical distribution of disease was assessed in three separate experiments in 2010 and 2011 (moderate and light scab years, respectively) on cvs. Desirable and Wichita. Samples of fruit were collected from trees at heights of 0-5, 5.0+-7.5, 7.5+-10, 10+-12.5 and 12.5+ m and assessed for disease. Disease was greatest <5m above ground, and least at heights >12.5 m. Disease severity was variable in the mid-section of trees. Disease severity is often greatest at the base of the canopy, and least at the apex of the tree, but the precise distribution likely depends on sources of inoculum, canopy architecture and the environment.

Technical Abstract: Pecan scab (Fusicladium effusum) is a destructive disease of pecan. There is concern that disease in the upper canopy of tall trees is difficult to control using ground-based sprayers. To establish a basic understanding of the distribution of scab in a non-treated pecan canopy, the vertical distribution of disease was assessed in three separate experiments in 2010 and 2011 (moderate and light scab years, respectively) on cvs. Desirable and Wichita. Samples of 5 or 10 leaves or fruit were collected from 4 replicate trees at heights of 0-5, 5.0+-7.5, 7.5+-10, 10+-12.5 and 12.5+ m and assessed for disease. General linear modeling demonstrated disease was greatest <5m above ground, and least at heights >12.5 m (F=2.55-12.3, P=<0.0001-0.04). Only on foliage of cv. Desirable in June 2011 was there no significant effect (F=0.86, P=0.9). However, disease severity was variable in the mid-section of trees. There was a slight but significant negative linear relationship between sample height and disease severity on fruit on cvs. Wichita and Desirable in August 2011 (P=0.04, R2=0.22 and P=0.0006, R2=0.49) and on Desirable in October 2011 (P=0.05, R2=0.20), but not on foliage on Desirable in 2010, or Wichita or Desirable in June 2011 or on fruit in October 2010. Disease severity is often greatest at the base of the canopy, and least at the apex of the tree, but the precise distribution likely depends on sources of inoculum, canopy architecture and the environment.