And just like that, the summer is over!

After three months of planting, spraying, inoculating, evaluating, and harvesting tomatoes, cucurbits, and peppers, our field season is coming to an end. It’s been a lot of work, and it’s been fun, and it’s been a lot of fun work. The upside of working in crop pathology is that you can literally reap the fruits of your labor, which we all enjoy.

With the exception of a major flooding event in Haywood and Henderson counties, it’s been a great season for growing tomatoes, and we had difficulty getting early blight, bacterial leaf spot, and gray leaf spot to spread in our disease trials. We attribute this to a relatively mild and dry growing season. However, the climate did not affect the arrival and spread of cucurbit downy mildew in our cucurbit trial, and some of our untreated plots were severely affected.

Our two trials evaluating bacterial leaf spot of pepper and Phytophthora blight of pepper were planted late, and are still underway, despite the efforts of local turkeys to uproot freshly-planted seedlings. We greatly appreciate the support from staff at the Mountain Research Station and the Mountain Horticulture Crops Research and Extension Center where we conduct our research. We could not do any of this work without them!

The on-farm trials evaluating the effect of different fumigants, fumigation depths, and plastic cover are currently being harvested, and ratings for disease and weed prevalence have been underway throughout the growing season. Now it’s time to consolidate data, write reports, debrief, and plan for next year’s projects.

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The season begins

Warm weather and longer days mark the beginning of the field season for the Meadow’s lab. We have tomato and pepper transplants in the greenhouse waiting to be transplanted into the field over the next several weeks. Our field research this year will be taking place at the Mountain Research Station in Waynesville, NC and at the Mountain Horticultural Crops Research and Extension Center in Mills River, NC.

As is usually the focus of our field research, the majority of our trials this summer are to evaluate pesticide spray programs for the control of vegetable diseases.

This year’s disease trials will evaluate spray programs for the management of:

  • Bacterial spot of tomato and pepper
  • Phytophthora blight of pepper
  • Gray leaf spot of tomato
  • Late blight of tomato
  • Early blight of tomato
  • Septoria leaf spot of tomato
  • Cucurbit Downy Mildew

Additionally, we are repeating our 2020 trial comparing the yield of two tomato scions (Mountain Gem and Jolene) grafted onto three different tomato rootstocks or non-grafted, and either pruned or not. Results from this trial will be combined with last year’s results and will be incorporated into a budget analysis. Results from this project will be included in an Extension publication, which will help growers make decisions on which plants and horticultural practices are the best option for them.

We are also collaborating with several labs at NC State to conduct on-farm trials assessing the use of fumigants to manage Verticillium wilt of tomato, root-knot nematodes, and weed populations.

We are excited to begin our busy season, and you can expect periodical updates regarding the progress of our research. If you would like more information regarding our research, please refer to the Contact Us section of our website.

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2020 Phytophthora Project Results

2020 was the final year of a three-year project evaluating annual and herbaceous perennial landscape plants for resistance or tolerance to Phytophthora root or crown rot. Due to the impracticality of existing management options, as well as a lack of information regarding the susceptibility of annual and herbaceous perennial ornamental landscape plants to this disease in the southeastern United States, we evaluated the performance of 59 cultivars of annuals and 53 cultivars of herbaceous perennials in Phytophthora-infested landscape beds across western and central North Carolina over a period of three years.

We identified 26 cultivars of annuals and 22 cultivars of herbaceous perennials that performed well and are recommended for Phytophthora-infested landscapes. Future work may re-evaluate the performance of these plants in other locations to strengthen recommendations. For details about study design, results, and acknowledgements, see this extension publication: https://content.ces.ncsu.edu/phytophthora-root-and-crown-rot-in-the-landscape

 

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2019 Phytophthora Project Results

Results are in from our 2019 study of Phytophthora on herbaceous ornamentals. See project details below for a full summary including detailed results. Summary results — Printable PDF 

Landscape bed with flowers at Mills River, NC

Project Summary: Several popular bedding plants are susceptible to Phytophthora root and crown rot, a soilborne plant pathogen that can cause devastating economic losses to the ornamental plant industry. Controlling the disease can be particularly difficult once the pathogen is established, making the use of resistant or tolerant plants ideal for infested landscapes.

In summer 2019, we evaluated 14 annuals and 16 herbaceous perennials (Table 1) to multiple species of Phytophthora. Some of the plant species and/or cultivars chosen for this study were re-evaluated from our 2018 study (https://content.ces.ncsu.edu/phytophthora-root-and-crown-rot-in-the-landscape). Three landscape beds were established in different regions of western North Carolina (Mills River, NC; Waynesville, NC; Salisbury, NC) and were infested with three species of Phytophthora known to cause disease of nursery crops. As disease symptoms progressed, symptomatic plants were harvested and processed to determine the presence of Phytophthora and/or other common diseases that may have been suspected.

Flowers in a raised landscape bed

Results: Fifteen cultivars of the evaluated annuals and twelve cultivars of the evaluated herbaceous perennials appeared excellent or good (Table 1) throughout the growing season (June 3 – September 20, 2019). Phytophthora was recovered from four cultivars of the evaluated annuals and four cultivars of the evaluated perennials and these plants were rated as Fair or Poor. Plants that in the ‘Other’ category had other problems and will need to be reevaluated to confirm resistance. This study provides evidence of 27 ornamental plant cultivars that can be used as acceptable alternatives in landscape beds infested with Phytophthora.

Table 1. List of annual and herbaceous perennial cultivars that were evaluated for tolerance or resistance to Phytophthora spp. from June 3 to September 20, 2019.

Ratinga Type Plant Species Cultivar Disease IDb
Excellent Annuals Angelonia (Angelonia angustifolia) ArchAngel Blue
Serenita White
Sweet Potato Vine (Ipomoea batatas) Ace of Spades
Tri-Color
West Indian Lantana (Lantana camara) Miss Huff
Lantana (Lantana hybrida) Little Lucky Pot of Gold
Little Lucky Peach Glow
African Marigold (Tagetes erecta) Antigua Yellow
Zinnia (Zinnia angustifolia) Star White
Star Orange
Perennials Hybrid Yarrow (Achillea filipendulina) Moonshine
Ornamental Sedge (Carex flacca) Blue Zinger
Ornamental Sedge (Carex testacea) Prairie Fire
Tickseed (Coreopsis auriculata) Nana
Coneflower (Echinacea purpurea) PowWow Wildberry
Cheyenne Spirit
Verbena (Glandularia canadensis) Homestead Purple
Ornamental Grass (Miscanthus sinensis) Little Zebra
Ornamental Grass (Panicum virgatum) Shenandoah
Rotstrahlbusch
Good Annuals Celosia (Celosia cristata) Dracula A, U
African Marigold (Tagetes erecta) Antigua Orange F
French Marigold (Tagetes patula) Janie Deep Orange A
Janie Spry A
Verbena hybrid (Verbena hybrida) Superbena Royal Chambray A
Perennials Rose mock vervain (Glandularia canadensis) Homestead Purple A
Peruvian mock vervain (Glandularia peruviana) EnduraScape Red A
Fair Annuals Verbena hybrid (Verbena hybrida) Lanai Upright Rose with Eye P
Annual vinca (Catharanthus roseus) Cora Cascade Lilac L, P
Cora Cascade Strawberry L
Poor Annuals Petunia (Petunia x hybrida) Night Sky P
Perennials Verbena hybrid (Verbena hybrida) Superbena Stormburst P
Alyssum (Alyssum wulfenianum) Golden Spring P
Yarrow (Achillea leisii) King Edward P
Other Annuals Lychnis (Lychnis arkwrightii) Orange Gnome A, U, P
Perennials Tickseed (Coreopsis verticillata) Starlight U
Sunfire U
Bee balm (Monarda didyma) Pardon My Cerise I, M
Pardon My Purple I, M
Balmy I, L, M, N
Black-eyed Susan (Rudbeckia hirta) Little Goldstar A, S

aDisease Rating Scale: Excellent = no disease symptoms, excellent floral quality, survived entire growing season. Good = minor disease symptoms, good floral quality, most survived entire growing season. Fair = moderate disease symptoms, less than half (<6) the plants died before end of growing season. Poor = severe disease symptoms, more than half (>6) the plants died before end of growing season. Other = more than half (>6) the plants had abiotic or unknown issues that prevented a fair trial of the cultivars resistance or tolerance to Phytophthora.

bDisease ID Letter Code: A: Abiotic, F: Fusarium, I: Insect, L: Leaf spot, M: Powdery Mildew, N: Nematodes (parasitic), P: Phytophthora, S: Southern Blight, U: Unknown

Future Implications: This project has been funded for an additional two years (2020-2021) by the Horticultural Research Institute. We plan to evaluate additional cultivars of annuals and herbaceous perennials in the upcoming growing season(s) and selecting plants based on input from NC landscapers and nursery growers.

Acknowledgements: We’d like to thank area specialized agents Amanda Taylor and Stacey Jones for their help with this project in its second year. We’d also like to thank the nurseries in North Carolina who generously provided plants that made this study possible: Hawksridge Farms, Metrolina Greenhouses, Hoffman Nursery, and King’s Nursery.

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Second year: Phytophthora on Herbaceous Ornamentals

We are on the second year of evaluating herbaceous ornamental plants for resistance or tolerance to Phythophthora root rot, crown rot, and foliar blight. We are repeating our study from 2018: A sustainable approach to Phytophthora-infested landscape beds and re-evaluating plant species and cultivars that had a performance rating of ‘Excellent’ or ‘Good’ from 2018. Additionally, we are evaluating new plant species and cultivars to make stronger recommendations for alternative plants that can be used in landscape beds infested with Phytophthora root rot, crown rot, and aerial blight.

Project Summary

Our study aims to provide a sustainable approach to landscapers by evaluating multiple cultivars of annuals and herbaceous perennials that are tolerant or resistant to Phytophthora. Plants were selected based on desirability and prior observations of tolerance or resistance to Phytophthora and other common diseases found in ornamental plants (ex. downy mildew, powdery mildew, etc.).

Three landscape beds were established to ensure consistency within the confines of one growing season. Each bed is established in:

  1. Mountain Horticultural Crops Research and Extension Center, Mills River, NC
  2. Mountain Research Station, Waynesville, NC
  3. Piedmont Research Station, Salisbury, NC

Each bed is approximately 200ft2 and filled with a blend of screened top soil and compost. To infest the soil, inoculum of three species of Phytophthora (P. nicotianaeP. drechsleriP. tropicalis) known to cause disease on herbaceous ornamentals will be added to each bed. Plants will be rated regularly for disease incidence and severity based on the percentage of the plant showing symptoms of root rot, crown rot, or aerial blight.

Click here to see the full list of plants we are evaluating in 2019

Enjoy some photos below and check back for project updates!

Planting the landscape bed at the Mountain Horticultural Crops Research and Extension Center

Planting the landscape bed at the Mountain Horticultural Crops Research and Extension Center on May 29, 2019

Landscape bed at the Mountain Horticultural Crops Research and Extension Center, Mills River, NC

Landscape bed at the Mountain Horticultural Crops Research and Extension Center, Mills River, NC

Landscape bed at the Piedmont Research Station, Salisbury, NC

Landscape bed at the Piedmont Research Station, Salisbury, NC

Landscape bed at the Mountain Research Station, Waynesville, NC

Landscape bed at the Mountain Research Station, Waynesville, NC

Amanda Scherer (Post-doc) is helping dig trenches in the soil before adding the Phytophthora inoculum

Amanda Strayer-Scherer (Post-doc) adding Phytophthora inoculum to the Piedmont Research Station landscape bed on June 13, 2019

Phytophthora inoculum going into the Piedmont Research Station bed on June 12, 2019.

Phytophthora inoculum going into the soil at the Piedmont Research Station bed on June 12, 2019

Stay tuned for project updates and results!

To learn more about Phytophthora on ornamental plants and how to manage for this disease, please view the NCSU Disease Fact Sheet for more information.

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