@article{scruggs_basaiah_adams_quesada-ocampo_2017, title={Genetic Diversity, Fungicide Sensitivity, and Host Resistance to Ceratocystis fimbriata Infecting Sweetpotato in North Carolina}, volume={101}, ISSN={["1943-7692"]}, DOI={10.1094/pdis-11-16-1583-re}, abstractNote={Black rot of sweetpotato, caused by Ceratocystis fimbriata, has recently reemerged as a significant threat to sweetpotato production in North Carolina and other states across the United States. This disease has historically been controlled largely through cultural management strategies and, in some cases, fungicide application. The sudden and destructive reemergence of this disease in 2015 created the need for rapidly evaluating disease control strategies. Genetic diversity of current C. fimbriata isolates infecting sweetpotato in North Carolina was assessed using ITS, TEF, and MAT-2 sequences. All 50 tested isolates were confirmed to be of a single mating type, MAT-2, based on PCR amplification. Alignment of ITS, TEF, and MAT-2 sequences revealed all isolates were identical at each locus. Fourteen common sweetpotato cultivars and advanced breeding lines were screened for black rot resistance using two isolates. None of the cultivars were completely resistant to the disease and most were equally susceptible. 'Stokes Purple' and 'Covington' were the least susceptible, but significantly (P < 0.05) differed only from 'Bellevue', the most susceptible cultivar. Sensitivity of 50 C. fimbriata isolates to difenoconazole, fludioxonil, thiabendazole, dicloran, azoxystrobin, pyraclostrobin, fenamidone, and fluazinam was evaluated in vitro. Difenoconazole, thiabendazole, and fluazinam were most effective in reducing mycelia growth. Postharvest fungicide application on black rot-infected roots provided similar results. Low efficacy of dicloran, as well as a range of EC50 values among isolates, suggests potential resistance to this commonly applied fungicide. Results obtained in this study provide current and useful information so that improved recommendations can be made to reduce losses in sweetpotato to black rot.}, number={6}, journal={PLANT DISEASE}, author={Scruggs, A. C. and Basaiah, T. and Adams, M. L. and Quesada-Ocampo, L. M.}, year={2017}, month={Jun}, pages={994–1001} }
 @article{scruggs_quesada-ocampo_2016, title={Cultural, Chemical, and Alternative Control Strategies for Rhizopus Soft Rot of Sweetpotato}, volume={100}, ISSN={["1943-7692"]}, DOI={10.1094/pdis-01-16-0051-re}, abstractNote={Rhizopus soft rot, caused primarily by Rhizopus stolonifer, is one of the most common postharvest diseases of sweetpotato and is often considered the most devastating. Traditionally, Rhizopus soft rot has been effectively controlled using postharvest dips in dicloran fungicides; however, due to changes in market preferences, use of these fungicides is now limited. This, along with the lack of labeled and effective fungicides for control of Rhizopus soft rot in sweetpotato, creates the need for integrated strategies to control the disease. The effects of storage temperature (13, 23, and 29°C), relative humidity (80, 90, and 100%), and initial inoculum levels (3-, 5-, and 7-mm-diameter mycelial plugs) on progression of Rhizopus soft rot in 'Covington' sweetpotato were examined. Percent decay due to Rhizopus soft rot infection was significantly reduced (P < 0.0001) at a low temperature (13°C) but was not significantly affected by changes in relative humidity or initial inoculum level (P >0.05). Sporulation of R. stolonifer was also significantly reduced at the lowest temperature of 13°C. High relative humidity (>95%) significantly increased sporulation of R. stolonifer and sporulation also increased as initial inoculum level increased. Efficacy of chlorine dioxide (ClO2) fumigation, UV-C irradiation, and postharvest dips in alternative control products were also investigated for control of Rhizopus soft rot. Static ClO2 treatments were effective in reducing sporulation on treated roots but had no significant impact on incidence of Rhizopus soft rot. UV irradiation at 3.24 KJ/m2 1 h after inoculation as well as dips in aqueous ClO2 and StorOx 2.0 significantly (P < 0.05) reduced disease incidence. Understanding the epidemiological factors favoring Rhizopus soft rot and identifying alternative control strategies allow for improved recommendations to limit postharvest losses in sweetpotato.}, number={8}, journal={PLANT DISEASE}, publisher={Scientific Societies}, author={Scruggs, A. C. and Quesada-Ocampo, L. M.}, year={2016}, month={Aug}, pages={1532–1540} }
 @article{scruggs_quesada-ocampo_2016, title={Etiology and Epidemiological Conditions Promoting Fusarium Root Rot in Sweetpotato}, volume={106}, ISSN={["1943-7684"]}, url={https://doi.org/10.1094/PHYTO-01-16-0009-R}, DOI={10.1094/phyto-01-16-0009-r}, abstractNote={Sweetpotato production in the United States is limited by several postharvest diseases, and one of the most common is Fusarium root rot. Although Fusarium solani is believed to be the primary causal agent of disease, numerous other Fusarium spp. have been reported to infect sweetpotato. However, the diversity of Fusarium spp. infecting sweetpotato in North Carolina is unknown. In addition, the lack of labeled and effective fungicides for control of Fusarium root rot in sweetpotato creates the need for integrated strategies to control disease. Nonetheless, epidemiological factors that promote Fusarium root rot in sweetpotato remain unexplored. A survey of Fusarium spp. infecting sweetpotato in North Carolina identified six species contributing to disease, with F. solani as the primary causal agent. The effects of storage temperature (13, 18, 23, 29, and 35°C), relative humidity (80, 90, and 100%), and initial inoculum level (3-, 5-, and 7-mm-diameter mycelia plug) were examined for progression of Fusarium root rot caused by F. solani and F. proliferatum on 'Covington' sweetpotato. Fusarium root rot was significantly reduced (P < 0.05) at lower temperatures (13°C), low relative humidity levels (80%), and low initial inoculum levels for both pathogens. Sporulation of F. proliferatum was also reduced under the same conditions. Qualitative mycotoxin analysis of roots infected with one of five Fusarium spp. revealed the production of fumonisin B1 by F. proliferatum when infecting sweetpotato. This study is a step toward characterizing the etiology and epidemiology of Fusarium root rot in sweetpotato, which allows for improved disease management recommendations to limit postharvest losses to this disease.}, number={8}, journal={PHYTOPATHOLOGY}, publisher={Scientific Societies}, author={Scruggs, A. C. and Quesada-Ocampo, L. M.}, year={2016}, month={Aug}, pages={909–919} }
 @article{quesada-ocampo_al-haddad_scruggs_buell_trail_2016, title={Susceptibility of Maize to Stalk Rot Caused by Fusarium graminearum Deoxynivalenol and Zearalenone Mutants}, volume={106}, ISSN={["1943-7684"]}, url={https://doi.org/10.1094/PHYTO-09-15-0199-R}, DOI={10.1094/phyto-09-15-0199-r}, abstractNote={Fusarium graminearum is a destructive pathogen of cereals that can cause stalk rot in maize. Stalk rot results in yield losses due to impaired grain filling, premature senescence, and lodging, which limits production and harvesting of ears. In addition, mycotoxins can make infected tissues unfit for silage. Our objectives were to evaluate the natural variation in stalk rot resistance among maize inbreds, to establish whether deoxynivalenol (DON)- and zearalenone (ZEA)-deficient strains are pathogenic on a panel of diverse inbreds, and to quantify the accumulation of DON in infected stalk tissue. Wild-type F. graminearum and mycotoxin mutants (DON and ZEA) were used to separately inoculate stalks of 9-week-old plants of 20 inbreds in the greenhouse. Plants were evaluated for lesion area at the inoculation point at 0, 2, 14, and 28 days postinoculation and tissues around lesions were sampled to determine the DON content. Regardless of their ability to produce DON or ZEA, all tested F. graminearum strains caused stalk rot; however, significant differences in disease levels were detected. Among the tested inbreds, Mp717 was resistant to all three F. graminearum strains while Mp317 and HP301 were only partially resistant. Accumulation of DON was significantly lower in infected stalks of the resistant and partially resistant inbreds than the susceptible inbreds. Analysis of the 20 inbreds using data from 17 simple-sequence repeats revealed population structure among the individuals; however, there was no association between genetic clustering and stalk rot resistance. These findings are an additional step toward breeding maize inbreds suitable for planting in fields infested with F. graminearum.}, number={8}, journal={PHYTOPATHOLOGY}, publisher={Scientific Societies}, author={Quesada-Ocampo, L. M. and Al-Haddad, J. and Scruggs, A. C. and Buell, C. R. and Trail, F.}, year={2016}, month={Aug}, pages={920–927} }
 @article{scruggs_butler_quesada-ocampo_2014, title={First Report of Cladosporium Leaf Spot of Spinach Caused by Cladosporium variabile in North Carolina}, volume={98}, ISSN={["1943-7692"]}, DOI={10.1094/pdis-05-14-0474-pdn}, abstractNote={Cladosporium leaf spot of spinach, caused by Cladosporium variabile, can result in significant economic losses in the United States (2). In March 2014, symptoms consistent with Cladosporium leaf spot (4) appeared on the spinach cultivar Tyee in a greenhouse located in Rowan County, NC. Of 1,080 spinach plants, 90 to 100% were infected. Symptoms consisted of small (1 to 3 mm in diameter), circular, tan lesions each outlined with a dark margin on the adaxial surface of the leaf. On severely infected foliage, lesions coalesced to produce relatively large necrotic regions. Profuse fungal sporulation was observed on the lesion surface with a dissecting microscope at 40× magnification. Using a dissecting microscope, conidia were collected with a sterile needle and transferred to petri plates containing potato dextrose agar. Plates were then incubated at 23 ± 2°C under continuous fluorescent light, and fungal growth was apparent after 24 h. Isolations from leaves of six infected plants produced slow-growing, dark green to brown fungal colonies that reached only 31 mm in diameter after 14 days, which is characteristic of C. variabile (4). Colonies contained dense masses of dematiaceous, septate, unbranched conidiophores with conidial chains, each containing up to five conidia. Conidia were ovate to elongate, with some being septate. The length of individual conidia ranged from 10 to 19 μm. Conidial septa were distinctly dark when observed at 100× magnification, which is a defining feature of C. variabile vs. the conidia of C. macrocarpum (4). The surface of the conidia appeared verrucose at 100× magnification, and conidia were each distinctly darkened toward the base. A single isolate obtained through single-spore transfer was used for DNA extraction, and the histone 3 (H3) gene sequence was amplified using the primers CYLH3F and CYLH3R (1). Sequence analysis of the amplified product using BLAST analysis indicated that the H3 sequences had 100% identity to that of a C. variabile isolate (GenBank Accession No. EF679710.1), and 99% identity to a C. macrocarpum isolate (EF679687.1). The H3 sequence from a representative isolate was deposited in GenBank (KJ769146). To our knowledge, this is the first report of Cladosporium leaf spot on spinach in North Carolina based on morphological evaluation and H3 sequencing results. C. variabile is a seedborne pathogen, so it is possible inoculum was introduced into the greenhouses in North Carolina on infected seed (3). Seeds can be treated with hot water or chlorine to reduce the risk of disease outbreaks caused by infected seed (2). Furthermore, Cladosporium leaf spot may be controlled with the use of fungicides (3). References: (1) P. Crous et al. Stud. Mycol. 50:415, 2004. (2) L. J. du Toit and P. Hernandez-Perez. Plant Dis. 89:1305, 2005. (3) L. J. du Toit et al. Fung. Nemat. Tests 59:V115, 2004. (4) Schubert et al. Stud. Mycol. 58:105, 2007.}, number={12}, journal={PLANT DISEASE}, publisher={Scientific Societies}, author={Scruggs, A. C. and Butler, S. C. and Quesada-Ocampo, L. M.}, year={2014}, month={Dec} }