Relative Effects of Demethylation-Inhibiting Fungicides on Late Leaf Spot of Peanut

Field experiments were conducted in Tifton, GA, in 2007, 2008, and 2016, and in Plains, GA, in 2016 to examine the effects of various demethylation-inhibiting (DMI) fungicides on late leaf spot (Nothopassalora personata) of peanut (Arachis hypogaea) and to determine the relative efficacy of the DMI fungicides compared with tebuconazole and the protectant fungicide chlorothalonil. In all trials, leaf spot control provided by tebuconazole, metconazole, tetraconazole, propiconazole, and flutriafol was inferior to that provided by chlorothalonil. However, prothioconazole was superior to chlorothalonil for control of leaf spot in all trials. These results indicated that reduced efficacy of tebuconazole for control of late leaf spot coincides with similar reductions in control with most other available DMI fungicides. However, superior leaf spot control obtained with prothioconazole relative to the other DMI fungicides and chlorothalonil implies that efficacy of tebuconazole is not indicative of the performance of all other DMI fungicides on this disease.

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Effect of In-Furrow Application of Fluopyram on Leaf Spot Diseases of Peanut

Plant Disease ◽

10.1094/pdis-01-21-0052-re ◽

2021 ◽

Author(s):

Albert Culbreath ◽

Robert Kemerait ◽

Timothy Brenneman ◽

Emily Cantonwine ◽

Keith Rucker

Keyword(s):

Arachis Hypogaea ◽

Leaf Spot ◽

Fungal Pathogens ◽

Field Experiments ◽

Resistance Management ◽

Feeding Damage ◽

Early Season ◽

Late Leaf Spot ◽

Frankliniella Fusca ◽

Tobacco Thrips

In peanut (Arachis hypogaea) production, in-furrow applications of the pre-mix combination of the SDHI fungicide/nematicide, fluopyram, and the insecticide, imidacloprid are used primarily for management of nematode pests and for preventing feeding damage on foliage caused by tobacco thrips (Frankliniella fusca). Fluopyram is also active against many fungal pathogens. However, the effect of in-furrow applications of fluopyram on early leaf spot (Passalora arachidicola) or late leaf spot (Nothopassalora personata) has not been characterized. The purpose of this study was to determine the effects of in-furrow applications of fluopyram + imidacloprid or fluopyram alone on leaf spot epidemics. Field experiments were conducted in Tifton, GA in 2015, 2016, and 2018-2020. In all experiments in-furrow applications of fluopyram + imidacloprid provided extended suppression of early leaf spot and late leaf spot epidemics compared to the nontreated control. In 2020, there was no difference between the effects of fluopyram + imidacloprid and fluopyram alone on leaf spot epidemics. Results indicated that fluopyram could complement early season leaf spot management programs. Use of in-furrow applications of fluopyram should be considered as an SDHI fungicide application for resistance management purposes.

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Applications of Mixtures of Copper Fungicides and Chlorothalonil for Management of Peanut Leaf Spot Diseases

Plant Health Progress ◽

10.1094/php-2001-1116-01-rs ◽

2001 ◽

Vol 2 (1) ◽

pp. 1 ◽

Cited By ~ 2

Author(s):

A. K. Culbreath ◽

T. B. Brenneman ◽

R. C. Kemerait

Keyword(s):

Arachis Hypogaea ◽

Leaf Spot ◽

Field Experiments ◽

Cercospora Arachidicola ◽

Copper Oxychloride ◽

Copper Hydroxide ◽

Cercosporidium Personatum ◽

Late Leaf Spot ◽

Copper Fungicides

Management of early leaf spot (Cercospora arachidicola) and late leaf spot (Cercosporidium personatum) of peanut (Arachis hypogaea) in the southeastern U.S. is dependent upon multiple applications of foliar fungicides. Field experiments were conducted from 1997 to 2000 to compare the efficacy of mixtures of copper hydroxide or copper oxychloride and reduced rates of chlorothalonil with that of full rates of chlorothalonil alone or chlorothalonil + propiconazole. In all tests, rates per ha of 0.70 kg of chlorothalonil + 0.70 kg of copper oxychloride or higher provided leaf spot control that was similar (P > 0.05) to that achieved with standard rates of chlorothalonil (0.84 kg/ha) + propiconazole (0.063 kg/ha). Application of chlorothalonil at 0.56 kg/ha + copper oxychloride at 0.56 kg/ha controlled leaf spot as well as (P > 0.05) chlorothalonil alone at 1.26 kg/ha in five of six tests in which that treatment was evaluated. In three of four tests in 1998 and 1999, application of chlorothalonil at 0.63 kg/ha + copper hydroxide at 0.63 kg/ha controlled leaf spot as well as chlorothalonil alone at 1.26 kg/ha. In both tests in 2000, application of chlorothalonil at 0.84 kg/ha + copper hydroxide at 0.63 kg/ha controlled leaf spot as well as chlorothalonil alone at 1.26 kg/ha. There were no consistent yield differences among the chlorothalonil, chlorothalonil + propiconazole, or chlorothalonil + copper treatments. Accepted for publication 8 November 2001. Published 16 November 2001.

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Influence of Broadleaf Weeds on Chlorothalonil Deposition, Foliar Disease Incidence, and Peanut (Arachis hypogaea) Yield

Weed Technology ◽

10.1017/s0890037x00041336 ◽

1997 ◽

Vol 11 (1) ◽

pp. 51-58 ◽

Cited By ~ 14

Author(s):

Stanley S. Royal ◽

Barry J. Brecke ◽

Frederick M. Shokes ◽

Daniel L. Colvin

Keyword(s):

Arachis Hypogaea ◽

Leaf Spot ◽

Field Experiments ◽

Yield Loss ◽

Disease Incidence ◽

Weed Biomass ◽

Late Leaf Spot ◽

Foliar Disease ◽

Weed Density ◽

Weed Plants

Field experiments were conducted at Jay and Marianna, FL in 1988 and 1989 to determine the effects of sicklepod, Florida beggarweed, and common cocklebur density on chlorothalonil deposition to peanut foliage, peanut foliar disease incidence, and peanut yield. At a density of four weed plants per 8 m of row, Florida beggarweed and sicklepod reduced chlorothalonil deposition on peanut foliage by 20%, while common cocklebur reduced fungicide deposition by 34%. At the same density, incidence of the foliar diseases early leaf spot and late leaf spot increased 10% with Florida beggarweed, 14% with sicklepod, and 20% with common cocklebur compared with weed-free peanut. The predicted peanut yield loss from a weed density of four plants per 8 m was 16 to 19% for Florida beggarweed, 23 to 25% for sicklepod, and 31 to 39% for common cocklebur. Weed biomass increased with increasing weed density.

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Management of Leaf Spot Diseases of Peanut With Prothioconazole Applied Alone or in Combination With Tebuconazole or Trifloxystrobin

Peanut Science ◽

10.3146/ps08-005.1 ◽

2008 ◽

Vol 35 (2) ◽

pp. 149-158 ◽

Cited By ~ 17

Author(s):

A. K. Culbreath ◽

R. C. Kemerait ◽

T. B. Brenneman

Keyword(s):

Arachis Hypogaea ◽

Leaf Spot ◽

Field Experiments ◽

Yield Response ◽

Cercospora Arachidicola ◽

Cercosporidium Personatum ◽

Late Leaf Spot ◽

Similar Series

Abstract Field experiments were conducted in Tifton and Plains, GA in 2001–2007 to determine the efficacy of prothioconazole on early leaf spot (Cercospora arachidicola) and late leaf spot (Cercosporidium personatum) of peanut (Arachis hypogaea). In five of six experiments, application of one or both rates (0.18 and 0.20 kg ai/ha) of prothioconazole in sprays 3–6 (chlorothalonil at 1.26 kg ai/ha in sprays 1, 2, and 7) provided leaf spot control superior to tebuconazole (0.23 kg ai/ha) in a similar regime, and superior to chlorothalonil at 1.26 kg ai/ha applied full season (seven times) in four of six experiments. In a similar series of six experiments, application of 0.085 kg ai/ha of prothioconazole + 0.17 kg ai/ha of tebuconazole provided better leaf spot control than tebuconazole (0.23 kg ai/ha) applied in regimes similar to those described above. Leaf spot control with prothioconazole + tebuconazole was similar to chlorothalonil applied at 1.26 kg ai/ha full season in five of eight experiments, but was less effective in the remaining three experiments. Fungicide effects on yield were inconsistent, but in all experiments, yield response with either rate of prothioconazole was similar to or greater than that obtained with 0.23 kg ai/ha tebuconazole on the same schedule. In a third series of four experiments, full-season (seven sprays) application of mixtures of prothioconazole at 0.063 kg ai/ha with trifloxystrobin at 0.063 kg ai/ha gave similar or better leaf spot control than chlorothalonil full season.

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Late Leaf Spot Severity and Yield of New Peanut Breeding Lines and Cultivars Grown Without Fungicides

Plant Disease ◽

10.1094/pdis-02-17-0165-re ◽

2017 ◽

Vol 101 (11) ◽

pp. 1843-1850 ◽

Cited By ~ 3

Author(s):

Brian S. Jordan ◽

Albert K. Culbreath ◽

Timothy B. Brenneman ◽

Robert C. Kemerait ◽

William D. Branch

Keyword(s):

Leaf Spot ◽

Vegetation Index ◽

Field Experiments ◽

Organic Production ◽

Canopy Reflectance ◽

Cercospora Arachidicola ◽

Early Season ◽

Late Leaf Spot ◽

Breeding Lines ◽

Width Measurements

Peanut (Arachis hypogaea) cultivars with resistance or tolerance to Cercospora arachidicola and/or Cercosporidium personatum, the causes of early and late leaf spot, respectively, are needed for organic production in the southeastern U.S. To determine the potential of new breeding lines for use in such production systems, field experiments were conducted in Tifton, GA, in 2014 and 2015 in which nine breeding lines and two cultivars, Georgia-06G and Georgia-12Y, were grown without foliar fungicide applications. In one set of trials, cultivar Georgia-12Y and most of the breeding lines evaluated had early season vigor ratings, early-season canopy width measurements, final plant populations, and pod yield that were greater than those of standard cultivar Georgia-06G. In those trials, final late leaf spot Florida scale ratings were lower and canopy reflectance measured as the normalized difference vegetation index (NDVI), was higher all the breeding lines than those of Georgia-06G. In another set of trials, two of those same breeding lines had final late leaf spot ratings similar to those of Georgia-12Y in 2014, whereas in 2015, six of those breeding lines had final leaf spot ratings that were lower than those of Georgia-12Y. Yields were similar for Georgia-12Y and all the breeding lines in the Gibbs Farm trials. Across years and breeding lines at the Lang Farm, the relationship between visual estimates of defoliation and NDVI was described by a two sector piecewise regression with NDVI decreasing more rapidly with increasing defoliation above approximately 89%. The utility of NDVI for spot comparisons among breeding lines appears to be limited to situations where there are differences in defoliation. Georgia-12Y and multiple breeding lines evaluated show potential for use in situations such as organic production where acceptable fungicides available for seed treatment and leaf spot control are limited.

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Efficacy of Organically Acceptable Fungicides for Management of Early and Late Leaf Spot Diseases on Partially Resistant Peanut Cultivars

Plant Health Progress ◽

10.1094/php-2008-0317-03-rs ◽

2008 ◽

Vol 9 (1) ◽

pp. 19 ◽

Cited By ~ 7

Author(s):

E. G. Cantonwine ◽

A. K. Culbreath ◽

B. B. Shew ◽

M. A. Boudreau

Keyword(s):

North Carolina ◽

Copper Sulfate ◽

Leaf Spot ◽

Field Experiments ◽

Disease Suppression ◽

Yield Response ◽

Cercospora Arachidicola ◽

Late Leaf Spot ◽

Cupric Hydroxide ◽

Affect Disease Severity

Field experiments were carried out in Georgia and North Carolina to evaluate the efficacy of fungicides approved for the organic management of early leaf spot, caused by Cercospora arachidicola, and late leaf spot, caused by Cercosporidium personatum, in peanut (Arachis hypogaea) fields planted to cultivars with partial resistance to one or both pathogens. Copper treatments alone or in mixtures resulted in less disease than a non-treated control. In Georgia, sulfur provided some disease suppression, but not as much as treatments with copper sulfate. Neem oil did not affect disease severity. Mean pod yields across years were significantly greater than the non-treated control only for copper sulfate in Georgia and cupric hydroxide in North Carolina. The minimal yield response to treatments suggests that under similar situations, the frequency of copper-based fungicide applications may be reduced with little affect on yield. Accepted for publication 16 January 2008. Published 17 March 2008.

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Management of Late Leaf Spot of Peanut with Benomyl and Chlorothalonil: A Study in Preserving Fungicide Utility

Plant Disease ◽

10.1094/pdis.2002.86.4.349 ◽

2002 ◽

Vol 86 (4) ◽

pp. 349-355 ◽

Cited By ~ 20

Author(s):

A. K. Culbreath ◽

K. L. Stevenson ◽

T. B. Brenneman

Keyword(s):

Leaf Spot ◽

Fungicide Resistance ◽

Field Experiments ◽

Resistance Management ◽

Model System ◽

Systemic Fungicide ◽

Cercospora Arachidicola ◽

Pathogen Population ◽

Late Leaf Spot ◽

Sterol Biosynthesis Inhibitor

Recent registration of sterol biosynthesis inhibitor and strobilurin fungicides for control of early (Cercospora arachidicola) and late (Cercosporidium personatum) leaf spot diseases of peanut (Arachis hypogaea) has renewed interest in the potential for loss of disease control due to fungicide resistance. The objectives of this study were to use the systemic fungicide benomyl, the protectant fungicide chlorothalonil, and late leaf spot of peanut as a model system to compare fungicide application strategies for fungicide resistance management. Field experiments were conducted at Tifton and Plains, GA, in 1995 and 1996 to determine the effects of alternate applications, mixtures, and alternating block applications of chlorothalonil and benomyl compared with full-season applications of two rates of chlorothalonil and two rates of benomyl alone on late leaf spot of peanut and on the proportion of the pathogen population resistant to benomyl following the various regimes. Tank mix combinations of half rates of the two fungicides and alternations of the full rates of the two fungicides provided better (P ≤ 0.05) control of late leaf spot than full-season applications of either rate of benomyl alone, and were comparable to full rates of chlorothalonil alone. Neither tank mixes nor alternating sprays prevented an increase in the relative frequency of benomyl-resistant isolates compared with other treatments in which benomyl was used. Both mixtures and alternate applications of chlorothalonil and benomyl were effective for management of leaf spot in fields where benomyl alone did not provide season-long leaf spot control.

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SSR analysis of cultivated groundnut (Arachis hypogaea L.) germplasm resistant to rust and late leaf spot diseases

Euphytica ◽

10.1007/s10681-006-9218-0 ◽

2006 ◽

Vol 152 (3) ◽

pp. 317-330 ◽

Cited By ~ 55

Author(s):

E. S. Mace ◽

D. T. Phong ◽

H. D. Upadhyaya ◽

S. Chandra ◽

J. H. Crouch

Keyword(s):

Arachis Hypogaea ◽

Leaf Spot ◽

Late Leaf Spot ◽

Ssr Analysis ◽

Arachis Hypogaea L

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Effect of In-Furrow and Early-Season Banded Applications of Fungicides on Incidence of Early Leaf Spot of Peanut

Plant Health Progress ◽

10.1094/php-rs-15-0029 ◽

2015 ◽

Vol 16 (4) ◽

pp. 225-229

Author(s):

Albert K. Culbreath ◽

Robert C. Kemerait ◽

Yun-Ching Tsai ◽

Timothy B. Brenneman ◽

Katherine L. Stevenson ◽

...

Keyword(s):

Arachis Hypogaea ◽

Leaf Spot ◽

Field Experiments ◽

Disease Incidence ◽

Cercospora Arachidicola ◽

Early Season ◽

Fungicide Application

Field experiments were conducted in Tifton, GA, in 2012-2014 to determine the effect of in-furrow applications of prothioconazole and early-season banded applications of prothioconazole or pyraclostrobin on incidence of early leaf spot (Cercospora arachidicola) of peanut (Arachis hypogaea). In each year, border rows were planted in May as a source of inoculum for plants in the treatment plots. Plots were planted in August or September after epidemics of early leaf spot were severe in the border plots. Fungicide application regimes included two rates (100 and 200 g a.i./ha) of prothioconazole applied in-furrow at planting, and 200 g a.i./ha of prothioconazole or 164 g a.i./ha of pyraclostrobin applied concentrated in a 30-cm band 21 days after planting (DAP). Incidence (percent of leaflets with one or more leaf spot) of early leaf spot was monitored until 54 to 57 days after planting in each year. In all years, disease incidence was below 10% at 28 DAP in plots treated with 200 g a.i./ha of prothioconazole in-furrow compared to over 40% in nontreated plots at the same time. In-furrow applications of 100 g a.i./ha of prothioconazole were less effective, but suppressed leaf spot incidence compared to the control. Banded applications of either fungicide at 21 DAP resulted in a decrease in leaf spot incidence, and prevented increase in leaf spot incidence for 19 days or longer. Accepted for publication 30 November 2015. Published 3 December 2015.

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