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ARS Home » Southeast Area » Byron, Georgia » Fruit and Tree Nut Research » Research » Publications at this Location » Publication #298906
Title: Trunk applications of phosphite for the control of pecan scab

Author
item Bock, Clive
item BRENNEMAN, TIM - University Of Georgia
item Hotchkiss, Michael - Mike
item Wood, Bruce

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 5/13/2013
Publication Date: 6/1/2013
Citation: Bock, C.H., Brenneman, T.B., Hotchkiss, M.W., Wood, B.W. 2013. Trunk applications of phosphite for the control of pecan scab. Phytopathology. 103:S2.17 http://apsjournals.apsnet.org/loi/phyto.

Interpretive Summary: Pecan scab (Fusicladium effusum) is the major disease of pecan in wet, humid climates. Management of scab can be challenging due to issues of fungicide resistance in F. effusum and management of the disease in tall trees due to the technical difficulties of getting sufficient spray coverage to the upper tree canopy. The feasibility of trunk application of phosphite, which is systemically transported, was investigated in six separate experiments in 2010 and 2011. Phosphite applied to trunks of young 3-4 year -old trees provided good control of scab on foliage. However, neither incidence nor severity of scab was reduced on older trees (>10 y) by trunk spray applications in 2010, although slightly less severe disease was indicated in 2011. Foliar sprays of phosphite and a conventional fungicide reduced the incidence and severity of fruit scab on most cultivars, confirming previous observations of the efficacy of these foliar sprays. Different methods of trunk phosphite application, for example trunk injection, might prove more efficacious than surface application in older trees.

Technical Abstract: Pecan scab (Fusicladium effusum) is the major disease of pecan in wet, humid climates. Management of scab can be challenging due to issues of fungicide resistance in F. effusum and management of the disease in tall trees due to the technical difficulties of getting sufficient spray coverage to the upper tree canopy. The feasibility of trunk application of phosphite, which is systemically transported, was investigated in six separate experiments in 2010 and 2011. Spray application of phosphite to trunks of young 3-4 year -old trees provided excellent control of scab on foliage of cultivar Desirable, but slightly poorer control on the susceptible cultivar Wichita. Neither incidence nor severity of scab was reduced on 11-12 year-old trees of cultivar Desirable by trunk spray applications in 2010, although slightly less severe disease was indicated in 2011. In two factorial cultivar*fungicide treatment experiments in 2010 and 2011 using 13-year-old trees there was little effect of trunk applications on scab incidence or severity on foliage or fruit. However canopy foliar applications of phosphite and a conventional fungicide significantly reduced the incidence and severity of fruit scab on most cultivars, confirming previous observations of the efficacy of these foliar sprays. Different methods of trunk phosphite application, for example trunk injection, might prove more efficacious than surface application in older trees.