About

Sara Villani is an Assistant Professor in the Department of Entomology and Plant Pathology at North Carolina State University. Her appointment is predominantly extension-focused, with 90% extension and 10% research. Her research efforts are directed towards addressing regional concerns of apple and woody ornamental stakeholders by developing novel and improved disease management practices. Her program integrates basic and applied research methods to create sustainable extension deliverables that are accessible and relevant to stakeholders, enabling informed decision-making in disease management. Her specific research goals include preserving single-site fungicides and antibiotics by mitigating resistance development, identifying cultural practices to reduce pathogen inoculum, understanding environmental and cultural factors involved in fungicide resistance, improving disease forecasting models, and assessing the impacts of global climate change on pathogen populations and disease management.

Research topics

• Genetics
• Botany
• Biology
• Microbiology
• Ecology
• Horticulture
• Biotechnology

Selected publications

• Field evaluation in the Eastern United States of a biological control Blossom Protect for fire blight suppression efficacy, potential to cause fruit russeting, and compatibility with fungicides

  Plant Disease · 2026-05-19

  article

  Fire blight is a destructive disease of apple and pear, and its severity is intensified under humid conditions. Biological controls are important components of the integrated management of plant diseases; however, field trials in the eastern United States have shown that currently available bacteria- and bacteriophage-based biocontrols lack the consistency and efficacy needed to meet industry standards under humid conditions. Blossom Protect is a yeast-based biocontrol agent developed for fire blight and post-harvest diseases of apple. Although Blossom Protect has shown effectiveness in the Pacific Northwest under the arid conditions, its efficacy has not yet been tested at a large scale in the eastern U.S. In this study, we conducted a multi-location, multi-season field evaluation of Blossom Protect to determine its effectiveness in suppressing fire blight. Blossom Protect consistently suppressed blossom blight incidence, with an average disease suppression determined at 63.9%, which exceeded that of oxytetracycline (57.1%) but remained lower than that of streptomycin (79.3%). The disease-suppression efficacy of Blossom Protect was further enhanced by the use of a contact sterilant, Oxidate, in an integrated management program. Blossom Protect increased fruit russeting; however, russeting was limited to 6-10% of the fruit surface on average and did not increase the proportion of out-of-grade fruit. We also assessed compatibility with fungicides commonly applied during bloom, and found Blossom Protect to be incompatible with conventional multi-site and quinone outside inhibitor (FRAC M and FRAC11) fungicides, as well as OMRI-listed contact sterilants and sulfur-based materials.

  PublisherDOI

• Maximizing the Biocontrol Potential of Bacteriophages: A Call for Critically-Needed Field Research

  Plant Disease · 2025-08-06 · 3 citations

  article

  Bacteriophages are viruses capable of infecting bacterial cells. Lytic phages, which infect and kill bacterial cells, are of interest in disease management in human, animal, and plant systems. In plant pathology, the biocontrol of bacterial diseases is of heightened interest because of the lack of efficacious options in many pathosystems. Numerous papers have been published in the past few decades on phage that target plant pathogenic bacteria, and a large majority of these have been focused on phage isolation and characteristics that highlight the promise and potential of phage as biocontrol agents. In contrast, relatively few of these papers have reported results from studies conducted in the field. Of the recent papers (2022 to 2025) reporting field studies, disease efficacy results are inconsistent. We argue that field studies should be an essential component of phage biocontrol research to understand how to best utilize and deploy phages to generate consistently effective disease management.

  PublisherDOI

• Evaluation of Biorational and Conventional Spray Applications for the Management of Fire Blight on ‘Gala’ Apple in North Carolina, 2023

  Plant Health Progress · 2025-01-01

  articleSenior author

  Fire blight, caused by the pathogen Erwinia amylovora, is a significant bacterial disease affecting pome fruit production globally. Symptoms include water soaking of floral tissue, blackening of leaf midribs, shoot wilt resembling a shepherd's crook, and at later stages may include lesions and wide-spread necrosis, potentially resulting in tree death. This report evaluates 11 different treatments consisting of individual or combined biorational and conventional treatments in addition to an untreated control group. The trial was conducted on 3-year-old Malus × domestica ‘Gala’ trees on G890 rootstock. Results from this trial provide will inform growers of potential antibiotic alternatives for the management of the blossom blight stage of fire blight disease in apple.

  PublisherDOI

• Prohexadione-calcium and Acibenzolar-S-methyl Effects and Interactions I: Vegetative Growth Management in a Young North Carolina Apple Orchard

  HortScience · 2025-09-03 · 2 citations

  articleOpen access

  Young apple ( Malus × domestica Borkh.) orchards are intensively managed to ensure successful orchard establishment. Use of growth retardants may aid in disease management; however, concerns regarding reduced bearing surface and increased time to full production are disincentives for use in young orchards. Prohexadione–calcium (P-Ca) is a gibberellin synthesis inhibitor used in apple to manage vigor and fire blight ( Erwinia amylovora ). Acibenzolar- S -methyl (ASM) is a systemic acquired resistance inducer used to induce an immune response in plants to protect against fungal and bacterial pathogens. The objective of the study was to apply different suggested rates of P-Ca and ASM alone and in combination to determine their impacts on shoot growth rate, tree size, canopy infill, and crop load. In 2021 to 2024, the study was conducted in a newly planted experimental ‘Gala’ orchard with a factorial treatment structure of two factors [P-Ca (0, 42.5, and 125 mg·L −1 ) and ASM (0 and 37.5 mg·L −1 )]. Treatments were applied twice each season, on the same plots each year to determine cumulative effects. As P-Ca rate increased, shoot growth rate and tree height decreased. Even with a decrease in tree size, canopy infill and linear bearing surface were maintained regardless of P-Ca or ASM rates. Fruit set was increased and return bloom decreased as P-Ca rate increased, but the addition of ASM lessened these effects. These results indicate that repeated applications of P-Ca on young orchards, in high-vigor locations, may reduce tree size, but not to a level that limits orchard establishment. P-Ca may increase fruit set, but ASM may have utility in lessening this effect and managing crop load.

  PublisherDOI

• Evaluation of Fungicides for the Management of Glomerella Leaf Spot and Bitter Rot on Apple in North Carolina

  Plant Disease · 2025-02-18 · 2 citations

  articleSenior author

  Glomerella leaf spot (GLS) and bitter rot caused by species in the Colletotrichum gloeosporioides species complex are the most economically devastating fungal diseases of apples in North Carolina. Crop losses have reached 100% in highly susceptible cultivars. In the southeastern United States, management of this disease has predominantly relied on broad-spectrum fungicide programs targeting several summer diseases of apples. To improve control of GLS and bitter rot, field experiments to evaluate the efficacy of multi- and single-site fungicides were conducted over multiple years in a ‘Gala’ research orchard in Mills River, NC, from 2017 to 2019. Fungicides representing different modes of action were applied in a nonrotational program from petal fall until the immediate preharvest period to assess their efficacy in reducing GLS incidence, shoot defoliation caused by GLS, and pre- and postharvest bitter rot. Of the fungicides evaluated, Captan 80WDG (active ingredient [a.i.] captan), Merivon (a.i. fluxapyroxad and pyraclostrobin), Cabrio (a.i. pyraclostrobin), and Aprovia (a.i. benzovindiflupyr) provided good to excellent control against disease caused by Colletotrichum chrysophilum. In these programs, the incidence of GLS, expressed as the relative area under the disease progress curve, ranged from 4.6 to 43.8 in the Captan 80WDG (2019) and the Aprovia (2017) programs, respectively. The incidence of bitter rot at harvest in these programs from 2017 to 2019 ranged from 0.0 to 45.3% in the 2018 and 2017 Captan 80WDG programs, respectively. Conversely, the highest incidences of GLS and preharvest bitter rot were consistently observed in the Inspire (a.i. difenoconazole), Sercadis (a.i. fluxapyroxad), and untreated programs. Shoot defoliation owing to GLS followed a similar trend across the evaluated fungicide programs. In addition to nonrotational fungicide programs, the effect of carrier water pH for applications of captan was evaluated for bitter rot control in Virginia and North Carolina. No differences in captan efficacy were observed at either location. The results of this study will inform the development of new management programs for GLS and bitter rot in the southeastern United States and provide a foundation for the development of new season-long fungicide programs for apple disease management.

  PublisherDOI

• Prohexadione-calcium and Acibenzolar-S-methyl Effects and Interactions II: Fire Blight Management in a Young North Carolina Apple Orchard

  HortScience · 2025-09-03 · 1 citations

  articleOpen access

  During apple ( Malus × domestica Borkh.) orchard establishment, fire blight outbreaks caused by Erwinia amylovora cause significant losses. The use of streptomycin is common; however, increased antibiotic resistance and public concern regarding pesticide safety necessitate alternative disease management solutions. Prohexadione-calcium (P-Ca) is a plant growth regulator that inhibits shoot growth and thickens cell walls, effectively reducing the penetration of bacteria into cells. Acibenzolar- S -methyl (ASM) is a systemic acquired resistance inducer that primes the immune system of a plant to allow for better defense when exposed to a pathogenic microorganism. The objective of this study was to determine the main effects and interactions of P-Ca and ASM on disease incidence and severity and bacterial population density in tissues with varying distances from the lesion edge. In 2022 and 2023, the study was conducted in a ‘Gala’ orchard in its second leaf and third leaf. Treatments were applied in a factorial treatment structure of two factors: 0, 42.5, and 125 mg·L −1 for P-Ca and 0 and 37.5 mg·L −1 for ASM. At the beginning of each season in 2021 to 2023, P-Ca and ASM were applied twice to the same plots each year. Shoot inoculations with E. amylovora occurred on 12 May 2022 and 11 May 2023. In 2022 and 2023, the P-Ca rate had a negative curvilinear relationship with disease incidence and severity across multiple dates. In 2022, ASM was variably impactful and interacted with P-Ca to lessen disease symptoms; however, this did not occur in 2023. On the final sampling date in 2023, bacterial density in the scion was lessened as the rate of P-Ca increased.

  PublisherDOI

• Evaluation of Biological and Conventional Fungicides for the Management of Marssonina Leaf Blotch on ‘Rome Beauty’ Apples in NC, 2023

  Plant Health Progress · 2025-01-01

  articleSenior author

  Marssonina leaf blotch (MLB) is a disease of apple caused by the fungal pathogen Marssonina coronaria. On foliage, MLB results in grayish-brown to purple leaf lesions, progressing into chlorosis and defoliation. This report evaluates the efficacy of both conventional and biological fungicides in controlling development of MLB symptoms. The trial was conducted at the Mountain Horticultural Crop Research and Extension Center in Mills River, NC, on 23-year-old Malus × domestica ‘Rome Beauty’ trees. Results from the trial will help advise growers in developing management programs for MLB, as well as provide insight into options for spray programs that utilize reduced loads of conventional fungicides.

  PublisherDOI

• Evaluation of Host Defense Inducers for the Management of Boxwood Blight Caused by <i>Calonectria pseudonaviculata</i> in North Carolina

  Plant Health Progress · 2025-11-21

  articleSenior author

  Boxwood blight, caused by the fungal pathogen Calonectria pseudonaviculata, has been reported in over 30 U.S. states and is a threat to boxwood production worldwide. Although considerable research has been conducted to evaluate the efficacy of conventional fungicides and cultural controls for this disease, the potential of host defense inducers remains largely unexplored. This study evaluated the effects of application method and frequency on managing boxwood blight in both container and field production systems in 2018 and 2019 at two locations in North Carolina. Actigard 50WG (acibenzolar- S-methyl) and LifeGard WG ( Bacillus mycoides isolate J) were applied as drench and foliar treatments to container-grown boxwoods artificially inoculated with C. pseudonaviculata and to field-grown boxwoods exposed to a natural inoculum. Drench applications of Actigard resulted in lower disease incidence than the untreated control plants under container production. High efficacy of Actigard was also observed under field production despite favorable environmental conditions for the development of boxwood blight. Application frequency did not affect disease for either of the tested host defense inducers in either production system. These findings support the integration of host defense inducers into cultural practice– and conventional fungicide–based management programs for boxwood blight.

  PublisherDOI

• Exotic ambrosia beetles and phytopathogenic fungi associated with rapid apple decline in North Carolina

  Journal of Economic Entomology · 2025-07-14 · 1 citations

  articleOpen accessSenior author

  Rapid apple decline is a syndrome primarily affecting young (<6 yr old) apple trees planted in high-density orchards throughout the eastern United States and Canada. Despite the sudden death of thousands of apple trees in North America, no definitive biotic or abiotic cause of rapid apple decline has been identified. Surveys of apple orchards in North Carolina experiencing rapid apple decline symptoms in 2017 found that ambrosia beetle infestations were associated with dead or declining trees. The exotic ambrosia beetles (Coleoptera: Scolytinae), Xylosandrus crassiusculus (Motschulsky) and X. germanus (Blandford), have been implicated in damage and decline of ornamental, fruit, and nut trees throughout the United States and are of increasing concern in other regions throughout the world. Trapping surveys across western North Carolina apple orchards over 3 yr revealed that X. crassiusculus, X. germanus, and Xyleborinus saxesenii (Ratzeburg) were the dominant species captured, with annual variation in species composition. The same 3 species of beetles were found inside the scion, rootstock, and graft union of declining apple trees collected from commercial orchards. A large diversity of fungi was associated with beetle gallery and non-gallery tissue on declining trees, including opportunistic phytopathogenic genera such as Botryosphaeria, Fusarium, and Diaporthe. No phytopathogenic fungi appeared to be exclusively associated with gallery tissue. The establishment of several genera of opportunistic fungal pathogens and ambrosia beetles in rapidly declining apple trees suggests that rapid apple decline in North Carolina has no single cause and is likely due to a combination of abiotic and biotic stress events.

  PublisherOA PDFDOI

• <i>Colletotrichum</i> Species Causing Glomerella Leaf Spot and Apple Bitter Rot in the Southeastern United States Exhibit Disparities in Relative Frequency, Morphological Phenotype, and Quinone Outside Inhibitor Sensitivity

  Plant Disease · 2024-09-16 · 3 citations

  articleSenior author

  Glomerella leaf spot (GLS), Glomerella fruit rot (GFR), and apple bitter rot (ABR), caused by Colletotrichum spp., are among the most devastating apple diseases in the southeastern United States. Although several species have been identified as causal pathogens of GLS, GFR, and ABR, their relative frequency and fungicide sensitivity status in the southeastern United States is unknown. In total, 381 Colletotrichum isolates were obtained from symptomatic leaves and fruit from 18 conventionally managed apple orchards and two baseline populations in western North Carolina and Georgia in 2016 and 2017. Multilocus DNA sequence analysis revealed that C. chrysophilum was the predominant cause of GLS and GFR and C. fioriniae was the causal agent of ABR. Baseline and commercial populations of Colletotrichum spp. were evaluated for sensitivity to pyraclostrobin and trifloxystrobin, and no statistical differences in sensitivity between the two species were observed for conidial germination. However, the effective concentration that inhibited growth by 50% values were significantly lower for C. fioriniae compared with C. chrysophilum for both fungicides regarding mycelial inhibition. Isolates recovered from commercial orchards revealed that five populations of C. chrysophilum and one population of C. fioriniae had reduced sensitivity to trifloxystrobin, and one C. fioriniae population had reduced sensitivity to pyraclostrobin via conidial germination assays. The cytb gene for 27 isolates of C. fioriniae, C. chrysophilum, and C. fructicola with different quinone outside inhibitor (QoI) sensitivities revealed the G143A mutation in a single isolate of C. chrysophilum with insensitivity to both fungicides. The results of these studies suggest that two Colletotrichum spp. predominantly cause GLS and ABR in the southeastern United States and that a reduction in sensitivity to some QoI fungicides may be responsible for control failures. This study also provides a basis for monitoring shifts in QoI sensitivity in Colletotrichum spp. causing disease on apple in the southeastern United States.

  PublisherDOI

Frequent coauthors

• Kerik D. Cox

  Cornell University

  81 shared

• Guido Schnabel

  Clemson University

  37 shared

• Anna Poniatowska

  Instytut Ogrodnictwa

  36 shared

• Katrin M. Ayer

  Cornell University

  9 shared

• Jessica J. Raes

  Cornell University

  7 shared

• Z. A. Frederick

  University of Florida

  6 shared

• Deborah Breth

  Cornell Cooperative Extension Association of Jefferson County

  6 shared

• I. J. Holb

  Centre for Agricultural Research

  6 shared

Labs

• Structural Pest Management Training & Research FacilityPI