@article{d'arcangelo_wallace_miles_quesada-ocampo_2022, title={Carboxylic Acid Amide but Not Quinone Outside Inhibitor Fungicide Resistance Mutations Show Clade-Specific Occurrence in Pseudoperonospora cubensis Causing Downy Mildew in Commercial and Wild Cucurbits}, volume={8}, ISSN={["1943-7684"]}, url={https://doi.org/10.1094/PHYTO-05-22-0166-R}, DOI={10.1094/PHYTO-05-22-0166-R}, abstractNote={Since its reemergence in 2004, Pseudoperonospora cubensis, the causal agent of cucurbit downy mildew (CDM), has experienced significant changes in fungicide sensitivity. Presently, frequent fungicide applications are required to control the disease in cucumber due to the loss of host resistance. Carboxylic acid amides (CAA) and quinone outside inhibitors (QoI) are two fungicide groups used to control foliar diseases in cucurbits, including CDM. Resistance to these fungicides is associated with single nucleotide polymorphism (SNP) mutations. In this study, we used population analyses to determine the occurrence of fungicide resistance mutations to CAA and QoI fungicides in host-adapted clade 1 and clade 2 P. cubensis isolates. Our results revealed that CAA-resistant genotypes occurred more prominently in clade 2 isolates, with more sensitive genotypes observed in clade 1 isolates, while QoI resistance was widespread across isolates from both clades. We also determined that wild cucurbits can serve as reservoirs for P. cubensis isolates containing fungicide resistance alleles. Finally, we report that the G1105W substitution associated with CAA resistance was more prominent within clade 2 P. cubensis isolates while the G1105V resistance substitution and sensitivity genotypes were more prominent in clade 1 isolates. Our findings of clade-specific occurrence of fungicide resistance mutations highlight the importance of understanding the population dynamics of P. cubensis clades by crop and region to design effective fungicide programs and establish accurate baseline sensitivity to active ingredients in P. cubensis populations.}, journal={PHYTOPATHOLOGY}, author={D'Arcangelo, K. N. and Wallace, E. C. and Miles, T. D. and Quesada-Ocampo, L. M.}, year={2022}, month={Aug} }
 @article{kimberly n. d'arcangelo_adams_kerns_quesada-ocampo_2021, title={Assessment of fungicide product applications and program approaches for control of downy mildew on pickling cucumber in North Carolina}, volume={140}, ISSN={["1873-6904"]}, url={https://doi.org/10.1016/j.cropro.2020.105412}, DOI={10.1016/j.cropro.2020.105412}, abstractNote={Pseudoperonospora cubensis, the causal agent of cucurbit downy mildew (CDM), is the most economically devastating and widespread disease of cucurbitaceous crops in the Eastern United States (US). Cucumbers are particularly susceptible and as a result, disease management of P. cubensis relies heavily on fungicide use. The re-emergence of P. cubensis in the US in 2004 resulted in the failure of previously effective host resistance and the pathogen has become less sensitive to several fungicides, limiting the efficacy of crop protection. The implementation of effective spray programs is recommended to minimize the development of fungicide resistance in pathogen populations. However, few studies have examined annual efficacy trials to generate robust recommendations. To determine the efficacy of fungicide applications on CDM in pickling cucumber regarding disease severity and marketable yield, field experiments were conducted from 2013 to 2016 in North Carolina. Evaluations included single-product fungicide applications as well as program treatments on susceptible cultivars. Although there was some variability between years due to differences in products applied, our analysis revealed that several single-site treatments were effective in the suppression of disease, including treatments that included oxathiapiprolin, cyazofamid, propamocarb, ethaboxam, fluazinam, and a mixture of mancozeb/zoxamide. Additionally, when compared to the non-treated controls, spray programs that included tank mixes with protectants and alternations of fungicide modes of action, resulted in lower levels of downy mildew and increased marketable yield.}, journal={CROP PROTECTION}, publisher={Elsevier BV}, author={Kimberly N. D'Arcangelo and Adams, Mike L. and Kerns, James P. and Quesada-Ocampo, Lina M.}, year={2021}, month={Feb} }
 @article{rahman_standish_d'arcangelo_quesada-ocampo_2021, title={Clade-Specific Biosurveillance of Pseudoperonospora cubensis Using Spore Traps for Precision Disease Management of Cucurbit Downy Mildew}, volume={111}, ISSN={["1943-7684"]}, url={https://doi.org/10.1094/PHYTO-06-20-0231-R}, DOI={10.1094/PHYTO-06-20-0231-R}, abstractNote={ Pseudoperonospora cubensis is an obligate oomycete and cause of cucurbit downy mildew (CDM), the most destructive foliar disease affecting cucurbit hosts. Annual epidemics develop throughout the United States as windborne sporangia travel great distances and survive prolonged exposure to solar radiation. Recent genomic evidence suggests that P. cubensis isolates display host adaptation based on their respective clade. Early detection is key for fungicide application timing, and identification of the host-adapted clade provides information on the risk of infection for specific cucurbit crops. In this study, a multiplex quantitative PCR assay was developed based on species- and clade-specific nuclear genomic markers. The assay detected as few as 10 sporangia or DNA at 100 fg/ml for both clades and was validated in the field by deploying rotorod spore samplers in cucurbit sentinel plots located at two research stations in North Carolina. Using this assay, sporangia DNA was detected in spore trap sampling rods before signs of P. cubensis or CDM symptoms were observed in the sentinel plots. Both clade 1 and clade 2 DNA were detected in late-season cucumber and watermelon plots but only clade 2 DNA was detected in the early-season cucumber plots. These results will significantly improve disease management of CDM by monitoring inoculum levels to determine the cucurbit crops at risk of infection throughout each growing season. }, number={2}, journal={PHYTOPATHOLOGY}, publisher={Scientific Societies}, author={Rahman, A. and Standish, J. R. and D'Arcangelo, K. N. and Quesada-Ocampo, L. M.}, year={2021}, month={Feb}, pages={312–320} }