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ARS Home » Southeast Area » Byron, Georgia » Fruit and Tree Nut Research » Research » Publications at this Location » Publication #296145
Title: Trunk applications of phosphite for the control of foliar and fruit scab

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

Submitted to: Crop Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/19/2013
Publication Date: 12/1/2013
Citation: Bock, C.H., Brenneman, T.B., Hotchkiss, M.W., Wood, B.W. 2013. Trunk applications of phosphite for the control of foliar and fruit scab. Crop Protection. 54:213-220.

Interpretive Summary: Pecan scab is the major disease of pecan in the south-eastern US. New efficaceous fungicides are needed to manage the disease. Furthermore it is technically difficult to get sufficient fungicide to the upper parts of the canopy in tall trees. The use of trunk application of phosphite, which is systemically transported within the tree, was investigated. Spray application of phosphite to the trunks of young 3-4 year -old trees provided good control of scab on foliage of cultivar Desirable and cultivar Wichita, but neither incidence nor severity of scab was reduced on older trees (>11 y-old) of cultivars Desirable, Cheyenne, Wichita or Apache. However canopy foliar application of phosphite and a conventional fungicide (triphenyl tin hydroxide) both significantly reduced the incidence and severity of scab on most cultivars on both foliage and fruit, confirming previous observations of the efficacy of these foliar sprays. Different methods of trunk application, for example trunk injections of phosphite, might prove more efficacious than surface application in older trees.

Technical Abstract: Pecan scab (Fusicladium effusum) is the major disease of pecan in the south-eastern US. Apart from issues of fungicide resistance and the need to test efficacy of novel fungicides such as phosphites, management of the disease in tall trees is challenging due to the technical difficulties of getting sufficient spray coverage to the upper parts of the canopy. The use of trunk application of phosphite, which is systemically transported within the tree, was investigated in six separate experiments in 2010 and 2011. Spray application of phosphite to the trunks of young 3-4 year -old trees provided excellent control of scab on foliage of cultivar Desirable, but slightly less good control on the susceptible cultivar Wichita, but neither incidence nor severity of scab was reduced on 11-12 year-old trees of cultivar Desirable was by trunk spray application 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 application of phosphite and a conventional fungicide both significantly reduced the incidence and severity of scab on most cultivars on both foliage and fruit, confirming previous observations of the efficacy of these foliar sprays. Different methods of trunk application, for example trunk injections of phosphite, might prove more efficacious than surface application in older trees.