Probabilities for Profitable Fungicide Use Against Gray Leaf Spot in Hybrid Maize

Abstract

Gray leaf spot, caused by the fungus Cercospora zeae-maydis, causes considerable yield losses in hybrid maize grown in the north-central United States and elsewhere. Nonchemical management tactics have not adequately prevented these losses. The probability of profitably using fungicide application as a management tool for gray leaf spot was evaluated in 10 field experiments under conditions of natural inoculum in Iowa. Gray leaf spot severity in untreated control plots ranged from 2.6 to 72.8% for the ear leaf and from 3.0 to 7.7 (1 to 9 scale) for whole-plot ratings. In each experiment, fungicide applications with propiconazole or mancozeb significantly reduced gray leaf spot severity. Fungicide treatment significantly (P </= 0.05) increased yield by as much as 1.65 t/ha with a single propiconazole application. There were significant (P < 0.05) correlations between gray leaf spot severity and yield. We used a Bayesian inference method to calculate for each experiment the probability of achieving a positive net return with one or two propiconazole applications, based on the mean yields and standard deviations for treated and untreated plots, the price of grain, and the costs of the fungicide applications. For one application, the probability ranged from approximately 0.06 to more than 0.99, and exceeded 0.50 in six of nine scenarios (specific experiment/hybrid). The highest probabilities occurred in the 1995 experiments with the most susceptible hybrid. Probabilities were almost always higher for a single application of propiconazole than for two applications. These results indicate that a single application of propiconazole frequently can be profitable for gray leaf spot management in Iowa, but the probability of a profitable application is strongly influenced by hybrid susceptibility. The calculation of probabilities for positive net returns was more informative than mean separation in terms of assessing the economic success of the fungicide applications.

Efficacy of Fungicides in Control of Fusarium oxysporum f. sp. dianthi, the Cause of Wilt in Carnation

“…Earlier reports suggested that the efficacy of propiconazole for disease control in several crop plants against various diseases. Propiconazole spray significantly reduced anthracnose of strawberry (Smith and Black, 1991), grey leaf spot of maize (Munkvold et al, 2001) and fungal leaf spots of rye grass (Koelsch et al, 1995). The fungicide propiconazole was the most important groups of fungicides (Baldwin and Rathmell, 1988).…”

Probability of Cost-Effective Management of Soybean Aphid (Hemiptera: Aphididae) in North America

“…The posterior distribution describes the knowledge about the parameter after the data are collected. Following Munkvold et al (2001), we present the probability that the yield gain from a treatment exceeded the GT at each of the four soybean prices. Given an appropriate choice of prior distributions, the posterior distribution of the difference in yield is a rescaled t-distribution (Box and Tiao 1973).…”

Viabilidade técnica e econômica da aplicação de estrobilurinas em milho

“…Nos últimos anos, o uso de fungicidas foliares em lavouras comerciais de milho tem aumentado de forma significativa nas principais regiões produtoras do Brasil e no mundo (Adee et al, 2005;Cunha et al, 2010;Juliatti et al, 2007;Munkvold et al, 2001;Pinto et al, 2004;Shah & Dillard, 2010). Tem sido bastante discutida e divulgada a existência de efeitos fisiológicos dos fungicidas do grupo das estrobilurinas em diversas culturas, inclusive no milho.…”

“…Algumas empresas têm divulgado o uso desses fungicidas para o manejo de estresses bióticos e abióticos em diversas culturas, sugerindo um potencial aumento de produtividade mesmo na ausência de doenças no campo (Rava, 2002;Wise & Mueller, 2011). No entanto, não se conhecem resultados de pesquisa quantificando esse potencial aumento da produtividade em milho advindo da utilização dos fungicidas estrobilurinas, e a magnitude dos benefícios econômicos desses fungicidas tem sido bastante questionada por parte de alguns patologistas de milho (Munkvold et al, 2001).…”