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ARS Home » Southeast Area » Byron, Georgia » Fruit and Tree Nut Research » Research » Publications at this Location » Publication #376443

Research Project: Healthy, Sustainable Pecan Nut Production

Location: Fruit and Tree Nut Research

Title: Rate of phosphonate affects control of scab on pecan

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

Submitted to: Pecan Grower
Publication Type: Trade Journal
Publication Acceptance Date: 5/17/2020
Publication Date: 6/1/2020
Citation: Bock, C.H., Brenneman, T.B., Brock, J.H., Herrington, K., Hotchkiss, M.W. 2020. Rate of phosphonate affects control of scab on pecan. Pecan Grower. 32:33-45.

Interpretive Summary: Trade article.

Technical Abstract: Scab, caused by the plant pathogenic fungus Venturia effusa, is the major disease of pecan in the southeastern USA. In widely grown susceptible cultivars, frequent application of fungicides is the only option to control the disease. Unfortunately, resistance to some fungicides has developed so management of the chemistries available is critical for the industry. 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 a total of six field experiments from 2015 to 2018 at two locations in Georgia. Cultivar Desirable was used in four experiments, and cv. Wichita was included in two years at one location. Depending on experiment, 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 10 sprays of phosphonate product were applied. Incidence of scab was invariably high on fruit from the non-treated, control trees and most often high on treated trees. However, 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. Regardless of epidemic intensity, higher rates of phosphonate provided more efficacious control. Phosphonate products are a vital chemistry to manage scab for the pecan industry in the southeastern USA and our results demonstrate that higher rates contribute to more efficacious control of this yield-limiting disease.