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IPM in soybean – investigations in pairing cultivars, fungicides, and application timings to maximize disease control and yield

Heather Kelly: University of Tennessee

<div>Can a more specific treatment plan be created for managing foliar diseases of soybean that encompasses cultivar, fungicide product, and application number and timing? To investigate this question, field trials arranged in a factorial design were conducted from 2014 through 2017 with 2-4 cultivars of varying disease resistance, multiple fungicides, single, double, and triple fungicide applications, and up to seven different application timings. Disease incidence and severity of frogeye leaf spot, septoria brown spot, and target spot were recorded along with yield. In trials conducted in 2014-2016, cultivars with greater resistance had greater yield, and the number of applications and application timing of fungicides had lower impact on yields compared to susceptible varieties. On average, a single application on resistant cultivars resulted in maximum yield, while susceptible cultivars benefited from additional fungicide applications. Although yield on susceptible cultivars was highest where three applications were made, only single and double fungicide applications increased the return on investment based on estimates of fungicide and application costs and commodity price. In 2017 trials, fungicide product significantly impacted yield, but there was no significant interaction between fungicide product and cultivar. Further results on yield and disease will be discussed along with economics associated with implementing specific treatment plan based on these data.</div>