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.

, 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.

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.

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.

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.

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.

Sensitivity of Cladosporium caryigenum to Propiconazole and Fenbuconazole.

Monoconidial isolates of the pecan scab fungus, Cladosporium caryigenum, were obtained in 1993 and 1994 from one pecan orchard each in Jeff Davis and Troup counties in Georgia, counties with no previous history of exposure to demethylation-inhibiting (DMI) fungicides. Isolates were grown on potato dextrose agar (PDA) amended with propiconazole or fenbuconazole at 0,0.0001, 0.