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ARS Home » Southeast Area » Byron, Georgia » Fruit and Tree Nut Research » Research » Publications at this Location » Publication #362737

Research Project: Mitigating Alternate Bearing of Pecan - Bridge Project

Location: Fruit and Tree Nut Research

Title: Higher rates of phosphonate improve efficacy against scab on pecan

item Bock, Clive
item BRENNEMAN, TIMOTHY - University Of Georgia
item HERRINGTON, KORY - University Of Georgia
item Hotchkiss, Michael - Mike

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 5/9/2019
Publication Date: 11/1/2019
Citation: Bock, C.H., Brenneman, T.B., Herrington, K., Hotchkiss, M.W. 2019. Higher rates of phosphonate improve efficacy against scab on pecan. Phytopathology. 109:S2.57.

Interpretive Summary:

Technical Abstract: Venturia effusa causes scab on pecan in the southeastern USA. In susceptible cultivars, frequent fungicide sprays is the only option to control the disease. Resistance to some fungicides has made management challenging. Understanding how rate affects disease control is important to ensure that control is maximized. We compared the effect of different rates of phosphonate products in reducing scab in six field experiments from 2015 to 2018 at two locations in Georgia. Cv. Desirable was used in four experiments, and cv. Wichita was included in two years at one location. Four rates of ProPhyt® (2.3, 3.5, 5.3 and 7.0 L/Ha), three rates of Rampart® (2.3, 4.7 and 7.0 L/Ha), or two rates of K-phite® 7LP (2.3 and 7.0 L/Ha) were tested. Also depending on experiment, 5 to 9 applications of phosphonate product were made. Incidence of scab was invariably high on fruit in the control trees, and most often high on treated trees. Treatment with the higher rates of phosphonate product most often significantly or numerically reduced severity of scab compared to the lower rates of the products applied on foliage and fruit. In 2015 fruit weight was increased where phosphonate application resulted in reduced disease, but in 2016 the effect was unclear due to a late and mild epidemic of scab likely having limited impact on the fruit size. Our results demonstrate that higher rates contribute to more efficacious control of this yield-limiting disease.