Efficiency and profitability of fungicides in controlling Bipolaris diseases and enhancing grain yield in cultivated wild rice (Zizania palustris)

Authors: CASTELL-MILLER, CLAUDIA - University Of Minnesota; Schlatter, Daniel; Samac, Deborah - Debby

Submitted to: Crop Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/2/2020
Publication Date: 3/1/2021
Citation: Castell-Miller, C.V., Schlatter, D.C., Samac, D.A. 2021. Efficiency and profitability of fungicides in controlling Bipolaris diseases and enhancing grain yield in cultivated wild rice (Zizania palustris). Crop Protection. 141. Article 105455. https://doi.org/10.1016/j.cropro.2020.105455.
DOI: https://doi.org/10.1016/j.cropro.2020.105455

Interpretive Summary: In 2015 there was an epidemic of leaf diseases in cultivated wild rice paddies across Minnesota that resulted in low grain yields to complete crop failure. There was a concern that the fungicides being use had lost efficacy. On-farm research was done in four locations over three years with five different fungicide combinations to test the efficacy of current practices. Overall, the fungicide treatments reduced leaf diseases and enhanced grain yields compared to the untreated control. There was an 85% probability overall that increased grain yield would offset the cost of fungicide application. On average, two fungicide applications had less risk than single sprays in offsetting costs. Together, these results indicate that current fungicides in use are profitable and efficient in reducing disease and enhancing grain yield in cultivated wild rice paddies. This information will assist growers in making economical crop management decisions.

Technical Abstract: In 2015 significant grain losses were observed in conjunction with high disease severity in cultivated wild rice (Zizania palustris) in Minnesota. The integrated disease management program included use of one or two fungicide sprays within the growing season. To test the efficiency of fungicide practices, on-farm trials were conducted in four Minnesota locations over two to three years using five fungicide combinations: QuiltXcel followed by Quadris (QX/Q), one early application of QuiltXcel (QX/-), early application of Quadris followed by Quadris (Q/Q), one early Quadris application (Q/-), and one late Quadris application (-/Q). Overall, disease severity was consistently reduced, and grain yield enhanced by fungicides compared to the non-treated control. A meta-analysis found the average disease effect sizes over all fungicide treatments were statistically significantly different (p–value = 0.0016) compared to the control. Grain yield effect sizes of treated plots were also superior to the control (p-value = 0.0061). Fungicide effect sizes on grain yield for QX/Q, QX/-, and Q/Q applications were statistically differently from the control with overall grain increases of 200 kg/ha (SEM = 46.7), 123 kg/ha (SEM = 50.2), and 179 kg/ha (SEM = 46.0), respectively. The probability of offsetting fungicide costs for the overall treatments was 85.5% but it differed by treatment from 57% (Q/-) to 87% (QX/Q). On average, two fungicide applications had less risk than single sprays in offsetting costs. Together, these results indicate that fungicide use is profitable and efficient in reducing disease and enhancing grain yield in cultivated wild rice paddies.