Mixing Elemental Sulfur or Chlorothalonil with QoI and DMI Fungicides for Management of Late Leaf Spot of Peanut.

Reduced sensitivity to demethylation inhibitor (DMI) and quinone outside inhibitor (QoI) fungicides in , the cause of late leaf spot of peanut (), complicates management of this disease in the Southeastern United States. Mixtures with protectant fungicides may help preserve the use of members of both DMI and QoI fungicide groups for leaf spot management. Field experiments were conducted in Tifton, GA, from 2019 to 2021 and in Plains, GA, during 2019 and 2020.

Functional Characterization of Core and Unique Calcite-Dissolving Bacteria Communities from Peanut Fields.

Calcium deficiency is a leading cause of reduced peanut () seed quality and has been linked to increased disease susceptibility, specifically to soilborne fungal pathogens. Sufficient calcium at flowering time is critical to ensure proper pod development. Calcite-dissolving bacteria (CDB) isolated from farming fields can dissolve calcite (CaCO) on plates and increase soluble calcium levels in soil.

Differences in distribution and community structure of plant-parasitic nematodes in pecan orchards between two ecoregions of Georgia.

In Georgia, pecans are commercially grown in the Piedmont and Coastal Plain ecoregions which are characterized by sandy-loam, sandy, and/or clay soils. If well-drained, these soils are suitable for pecan production, but the soil characteristics differ enough between ecoregions in which the plant-parasitic nematode (PPN) communities could differ substantially. We studied PPN communities in pecan orchards to evaluate the potential for ecoregion differences.

Effects of Field Fumigation and Inoculation With the Pecan Truffle () on the Fungal Community of Pecan () Seedlings Over 5 Years.

Truffle fungi are esteemed for their aromatic qualities and are among the most widely cultivated edible ectomycorrhizal fungi. Here we document a successful method for establishing , the pecan truffle, on pecan () seedlings in a field setting. We assessed the impacts of soil fumigation and varying concentrations of truffle spore inoculum on the ectomycorrhizal fungal and the complete fungal communities as well as the colonization of on pecan roots at three nurseries in Georgia, United States.

Sensitivity of Isolates from Peanut Seeds in Georgia to Azoxystrobin, a Quinone outside Inhibitor (QoI) Fungicide.

infects peanuts and produces a mycotoxin called aflatoxin, a potent human carcinogen. In infected peanuts, it can also affect peanut seed quality by causing seed rot and reducing seed viability, resulting in low germination. In 2020, peanut seeds in Georgia had lower than expected germination and a high frequency of contamination.

, a new species causing leaf dieback disease of pecan ().

species are endophytes and pathogens of woody hosts and members of the Botryosphaeriaceae. Leaf dieback is a new disease resulting in death of compound leaves and extensive defoliation of pecan trees () throughout the southeastern United States. Currently, the disease is consistently most severe on trees that are not managed with fungicides for pecan scab.

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

In peanut () production, in-furrow applications of the premix combination of the succinate-dehydrogenase-inhibitor (SDHI) fungicide and 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 (). Fluopyram is also active against many fungal pathogens. However, the effect of in-furrow applications of fluopyram on early leaf spot () or late leaf spot () has not been characterized.

Fungicide Resistance in , Cause of Pecan Scab: Current Status and Practical Implications.

Pecan scab, caused by , is the most economically damaging disease of pecan in the southeastern United States, and annual epidemics are most effectively managed through multiple fungicide applications. The fungicide applications can be the single greatest operating cost for commercial growers and the return on that investment is impacted by fungicide resistance. produces multiple generations of conidia per season, exhibits substantial genetic diversity, overwinters as stromata in the tree, and is under immense selection from the applied fungicides, all of which lead to a high risk for developing fungicide resistance.

Spatial Variation and Temporal Dynamics of Fungicide Sensitivity in Within a Pecan Orchard.

An 18-ha commercial pecan orchard was sampled over 3 years to study the spatial and temporal variation in fungicide sensitivity of , cause of pecan scab. The orchard was divided into a two-dimensional, 8 × 8 grid of 64 quadrats, each containing nine trees (unless there were missing trees), and samples were collected once per year from each quadrat to be tested for sensitivity to fentin hydroxide, propiconazole, and thiophanate-methyl. Averaged across the orchard, insensitivity to all three fungicides was significantly lower in 2016 compared with 2015, but significantly greater for fentin hydroxide and thiophanate-methyl in 2017.

Mapping quantitative trait loci (QTLs) and estimating the epistasis controlling stem rot resistance in cultivated peanut (Arachis hypogaea).

A total of 33 additive stem rot QTLs were identified in peanut genome with nine of them consistently detected in multiple years or locations. And 12 pairs of epistatic QTLs were firstly reported for peanut stem rot disease. Stem rot in peanut (Arachis hypogaea) is caused by the Sclerotium rolfsii and can result in great economic loss during production.

Relating Peanut Rx Risk Factors to Epidemics of Early and Late Leaf Spot of Peanut.

Previous research has demonstrated the efficacy of prescription fungicide programs, based upon Peanut Rx, to reduce combined effects of early leaf spot (ELS), caused by (), and late leaf spot (LLS), caused by (syn. ), but the potential of Peanut Rx to predict each disease has never been formally evaluated. From 2010 to 2016, non-fungicide-treated peanut plots in Georgia and Florida were sampled to monitor the development of ELS and LLS.

Disease and Yield Response of a Stem-rot-resistant and -Susceptible Peanut Cultivar under Varying Fungicide Inputs.

Peanut ( L.) producers rely on costly fungicide programs to manage stem rot, caused by . Planting disease-resistant cultivars could increase profits by allowing for the deployment of less-expensive, lower-input fungicide programs.

Assessing Fitness Costs and Phenotypic Instability of Fentin Hydroxide and Tebuconazole Resistance in .

Sensitivity monitoring of , cause of pecan scab, has revealed insensitivity to fentin hydroxide and tebuconazole, but recent research indicates that the insensitivity to fentin hydroxide is not stable. A study was undertaken to determine if a fitness cost may be responsible for this instability. In this study, experiments were conducted to evaluate fitness components and phenotypic stability of insensitivity of to fentin hydroxide and tebuconazole.

Effect of Planting Date and Peanut Cultivar on Epidemics of Late Leaf Spot in Georgia.

Field trials were conducted in 2015 and 2016 in Tifton, GA to determine the effects of planting dates (24 and 27 April, 4, 11, 19, and 26 May 2015; and 11, 18, and 25 April and 2, 9, and 16 May 2016), peanut () cultivar (Georgia-06G and Georgia-12Y), and seed treatment (nontreated and treated with azoxystrobin, fludioxonil, and mefenoxam) on epidemics of late leaf spot (), plant populations, and peanut yield. Final severity and AUDPC of late leaf spot increased with later planting dates in both years. For most planting dates in 2015 and the final planting date in 2016, final leaf spot severity and AUDPC were lower for Georgia-12Y than for Georgia-06G.

Quantifying the Effects of a G137S Substitution in the Cytochrome of on Azoxystrobin Sensitivity Using a Detached Leaf Assay.

The quinone outside inhibitor (QoI) fungicides are known for their inherently high resistance risk owing to substitutions in amino acid residues 129, 137, or 143 of the cytochrome gene of phytopathogens. In , cause of pecan scab, an intron adjacent to position 143 likely reduces this risk; however, the effects of a recently discovered substitution at position 137 (G137S) are unknown. Traditional in vitro assays are not useful for determining sensitivity of isolates of to the QoI fungicides, owing to the fungitoxic effects of required alternative oxidase inhibitors.

Dynamics of Fungicide Sensitivity in Venturia effusa and Fungicide Efficacy under Field Conditions.

Venturia effusa, which causes pecan scab, has developed resistance to fungicides that were once effective. Over 2 years, laboratory-based sensitivity of fentin hydroxide (TPTH) and tebuconazole in V. effusa and their efficacy under field conditions were compared.

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

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.

Severity of Scab and its Effects on Fruit Weight in Mechanically Hedge-Pruned and Topped Pecan Trees.

Scab is the most damaging disease of pecan in the southeastern United States. Pecan trees can attain 44 m in height, so managing disease in the upper canopy is a problem. Fungicide is ordinarily applied using ground-based air-blast sprayers.

Location of an Intron in the Cytochrome b Gene Indicates Reduced Risk of QoI Fungicide Resistance in Fusicladium effusum.

Pecan scab, caused by Fusicladium effusum, is most effectively managed using multiple fungicide applications, including quinone outside inhibitors (QoIs). However, QoIs have a high risk for resistance developing in phytopathogenic fungi. QoI resistance is generally associated with amino-acid substitutions at positions 129, 137, and 143 of the cytochrome b (cytb) gene.

Identification of genes differentially expressed during early interactions between the stem rot fungus (Sclerotium rolfsii) and peanut (Arachis hypogaea) cultivars with increasing disease resistance levels.

Sclerotium rolfsii, a destructive soil-borne fungal pathogen causes stem rot of the cultivated peanut, Arachis hypogaea. This study aimed to identify differentially expressed genes associated with peanut resistance and fungal virulence. Four peanut cultivars (A100-32, Georgia Green, GA-07W and York) with increasing resistance levels were inoculated with a virulent S.

Management of Daylily Rust with Different Fungicide Combinations and Spray Intervals.

Daylily (Hemerocallis spp.) is a popular herbaceous perennial plant and was considered to be relatively disease free until 2000, when daylily rust, caused by Puccinia hemerocallidis, was first detected in the United States. Management of daylily rust in nurseries is dependent on the use of fungicides, which are typically applied to the foliage of large blocks of plants at 21- or 28-day intervals.

First Report of Bacterial Blight of Sugar Beet Caused by Pseudomonas syringae pv. aptata in Georgia, USA.

Sugar beet (Beta vulgaris L.) is not currently a commercial crop in Georgia, but experimental plantings as a winter rotational crop are promising in terms of yield and industrial sugar production (T. Brenneman, personal communication).

First Report of Pythium deliense Associated with Peanut Pod Rot in Georgia.

In fall 2012 and 2013, peanut (Arachis hypogaea L.) grown in commercial fields in Tift County, GA, showed pod rot symptoms. The disease was primarily damaging pods and kernels and symptoms included brown to black, water-soaked lesions on pods and blackened pegs with white fluffy mycelia.