An Overview of Frogeye Leaf Spot

Wise, Kiersten; Bradley, Carl A.; Sikora, Ed; Mueller, Daren; Chilvers, Martin I.; Giesler, Loren J.; Smith, Damon; Tenuta, Albert

doi:10.31274/cpn-20190620-013

Cited by 5 publications

(15 citation statements)

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“…The lesion diameters range from 1 to 5 mm (Grau et al, 2004). On the abaxial surface, the formation of clusters of conidia can be observed in the center of mature lesions (Wise & Newman, 2015) (Figure 1.1B).…”

Section: Disease Symptomsmentioning

confidence: 99%

“…Although Cercospora sojina K. Hara is recognized as the causal agent of FLS, early literature reported Cercospora daizu as the causal agent of this disease (Athow, 1987). Conidia are hyaline, elongate to fusiform and measure 6-8 x 40-60 μm (Wise & Newman, 2015).…”

Section: Morphological Characterizationmentioning

confidence: 99%

“…Additionally, conidia can be produced on infected parts of the plant (leaf, stem, or seeds) and from infested residue on the soil surface (Cruz & Dorrance, 2009). As conidiophores continue to grow, conidia are formed on the tips and are pushed aside (Groenewald et al, 2012;Wise & Newman, 2015). In a single lesion, 2 to 25 conidiophores can be produced, and each conidiophore can produce 1 to 11 conidia (Lehman, 1928).…”

Section: Morphological Characterizationmentioning

confidence: 99%

“…Although disease symptoms most commonly appear during reproductive growth stages, FLS lesions can affect leaves, pods and stems at any stage of development (Wise & Newman, 2015).…”

Section: Disease Symptomsmentioning

confidence: 99%

“…Symptoms include small, dark lesions that evolve from tan to brown spots surrounded by a narrow, purple-brown margin (Wise & Newman, 2015) (Figure 1.1A). The lesion diameters range from 1 to 5 mm (Grau et al, 2004).…”

Section: Disease Symptomsmentioning

confidence: 99%

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Epidemiology and management of frogeye leaf spot of soybean: damage thresholds, efficacy and profitability of foliar fungicides

Barro¹

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Frogeye leaf spot (FLS), caused by Cercospora sojina, is an economically important disease of soybean in many parts of the world where soybean is grown, including the United States. A meta-analytic approach was used to summarize a data set of 66 uniform field research trials conducted to evaluate fungicide efficacy against FLS on soybean. The dataset spanned 10 years (2012 to 2021) of experiments conducted across eight states in the U.S., including Alabama, Arkansas, Illinois, Iowa, Kentucky, Louisiana, Mississippi and Tennessee. First, the relationship between FLS severity and soybean yield was investigated. A significant negative slope obtained through random effects meta-analytic models confirmed the negative linear relationship between FLS severity and soybean yield. Additionally, the overall relative damage coefficient was calculated to be 0.51%. In addition, economic damage thresholds were estimated by using the damage coefficient, for a range of soybean prices and control costs, taking into account three different fungicide efficacies (25%, 50% and 75%). The threshold values increased as the control efficacy also increased and were affected by different crop prices and fungicide costs. Second, the best fungicide options to control the disease were investigated. The results demonstrated that fungicide efficacy against FLS differ among active ingredients and is decreasing over time possibly due to fungicide resistant populations (mainly to the quinone outside inhibitors [QoIs]). The best performing fungicide reported in this study was a mixture of difenoconazole + pydiflumetofen, and the poorest performing fungicide was pyraclostrobin, a QoI fungicide. A statistically significant (P<0.05) decline in performance was detected for two fungicide mixtures (azoxystrobin + difenoconazole and thiophanate-methyl + tebuconazole) and two single active ingredients (pyraclostrobin and tetraconazole). Greater yields in trials with conditions favorable for severe epidemics were found, which could be explained by the more evident effect of the fungicides among the treated plots when compared to the nontreated control. Accordingly, the most effective treatments were more likely to be profitable under higher disease pressure and, as expected, the less effective treatment reported the higher risk of not offsetting the costs. Third, the profitability of applying fungicides was investigated in the absence or very low levels of FLS in double-crop soybean by using a different data set of 22 fungicide trials conducted between 2008 and 2021 across five states in the U.S. (Illinois, Indiana, Kentucky, Missouri, and Tennessee). The results showed no significant difference in yield response between the fungicide treatments and the nontreated control. Economic analyses indicated that, due to the lower yield responses, probabilities of breaking even were less than 50% for all the single fungicide classes, or up to 51% for mixtures, depending on fungicide cost and soybean price values. Overall, these research findings may provide useful information for regional risk assessment of potential yield loss caused by FLS, and for planning fungicide programs to control this important foliar disease. Decisions on fungicide planning must take into account, not only technical information such as control efficacy and yield return, but also profitability and strategies to mitigate fungicide resistance issues. Keywords: Cercospora sojina. Chemical control. Economic risk. Fungicide. Glycine max. Yield loss.

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Section: Disease Symptomsmentioning

confidence: 99%

Section: Morphological Characterizationmentioning

confidence: 99%

Section: Morphological Characterizationmentioning

confidence: 99%

“…Although disease symptoms most commonly appear during reproductive growth stages, FLS lesions can affect leaves, pods and stems at any stage of development (Wise & Newman, 2015).…”

Section: Disease Symptomsmentioning

confidence: 99%

Section: Disease Symptomsmentioning

confidence: 99%

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Epidemiology and management of frogeye leaf spot of soybean: damage thresholds, efficacy and profitability of foliar fungicides

Barro¹

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Frogeye leaf spot caused by Cercospora sojina: A review

Barro

Neves

Ponte

et al. 2023

Trop. plant pathol.

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Frogeye leaf spot (FLS), caused by Cercospora sojina, is an economically important disease of soybean in many parts of the world where soybean is grown, including the United States and Argentina. Yield losses caused by FLS epidemics are mainly due to reduced photosynthetic leaf area, premature defoliation and reduced seed weight. Epidemics may be initiated from inoculum produced on infected plant residue where the pathogen can overwinter for up to two years. Many questions relating to population biology, genetic variability and pathotype structure remain unanswered. Race designations for C. sojina are under debate since the use of the 12 soybean differentials has produced inconsistent numbers of races in separate studies. Although a sexual stage for C. sojina has not been observed in either field or laboratory conditions, equal proportion of mating-type loci and high genotypic diversity suggest that populations of C. sojina are most likely to be undergoing cryptic sexual reproduction. Management practices for this disease include the use of cultivars with partial or complete resistance (Rcs genes), cultural practices (crop rotation and tillage) and foliar fungicide applications. However, resistance to quinone outside inhibitor (QoI) fungicides (caused by the G143A mutation in the Cytochrome b gene) has been reported since 2010, and resistant populations have become widespread across more than 20 soybean-producing states in the U.S. This review provides detailed information on the taxonomy, identification and genetic diversity of the pathogen. It also summarizes epidemiological aspects and strategies to combat this increasing threat to soybean crops worldwide.

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Comparison of quinone outside inhibitor fungicide-resistant and -sensitive isolates of Cercospora sojina

Zhang

Bradley

2017

Crop Protection

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An Overview of Frogeye Leaf Spot

Cited by 5 publications

References 0 publications

Epidemiology and management of frogeye leaf spot of soybean: damage thresholds, efficacy and profitability of foliar fungicides

Epidemiology and management of frogeye leaf spot of soybean: damage thresholds, efficacy and profitability of foliar fungicides

Frogeye leaf spot caused by Cercospora sojina: A review

Comparison of quinone outside inhibitor fungicide-resistant and -sensitive isolates of Cercospora sojina

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