2023 Plant Disease and Insect Clinic Year in Review

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We’ve finally analyzed our 2023 samples and results, and we’re excited to share them!
In total the Plant Disease and Insect Clinic and Turf Diagnostic Lab received 2,899 sample submissions last year, only a slight decrease (1%) from 2022. Excluding the turf, ornamental grasses, and sedges, the number is 2,403, a very slight decrease (0.5%) from 2022. Of all the samples coming to both labs, 2,531 (87%) came from within the state of North Carolina.
Note that most of these summaries do not include turf samples. For a summary of 2023 from the NC State Turf Diagnostic Lab, please see their annual review.
Samples came from every county last year, with numerous counties submitting multiple samples throughout the year. Wake county submitted the most sample with 342. Here are the counties that submitted the most samples:

Top counties by samples submitted excluding turf: Wake 342, Orange 125, Buncombe 93, Mecklenburg 84, New Hanover 82, Henderson 69, Guilford 68, Johnston 68, Durham 56, Nash 51, Macon 43, Harnett 41, Wilson 41, Moore 40, Franklin 39, Pender 39, Cabarrus 38

As expected, the summer months were the busiest, with the lab receiving more than 300 samples in both June and July. At 322 samples total, July averaged around 16 samples per day

Number of samples by month entered: January 107, February 111, March 199, April 212, May 286, June 313, July 322, August 294, September 219, October 159, November 113, December 68

Samples can consist of images only, physical samples only, or a combination of both. In 2023, most samples were physical only (44%), followed by image-only samples (29%), then a combination of both (27%). Results were similar to 2022, except there were slightly more samples with both images and physical material, and fewer image-only samples.

Samples by type: both physical and image 27%, image only 29%, physical only 44%

These samples were submitted by different types of clients. Although direct submissions by clients made up 33% of all submissions, the remaining samples were submitted by state agricultural extension agents, various consultants, or a combination of them. The breakdown is very similar to 2022.

Samples by contact type: client alone 33%, NCCES Agent 39%, consultant private or NCDA 22%, and both agent and consultant 6%

The majority of samples (including those for turf) came from home grounds (32%), followed by crops in the field (20%), greenhouses (13%), golf courses (11%), container nurseries (6%), and commercial grounds or households (both tied at 5%). Household samples dropped a bit from 2022, but this is likely because we discontinued our mold identification service.

Samples by host site type: Home Grounds 32%, Field Crops 20%, Greenhouse 13%, Golf Course 11%, Container Nursery 6%, Commercial Grounds 5%, Household 5%, Field Grown Nursery 2% Orchard/Vineyard 1%, Forest/Plantation 1%, Park/Natural Area 1%, Aquatic Site 0.5%, All other or Not Provided 3%

The most common types of hosts submitted were trees and shrubs (28%), followed by field crops (16%), turf and ornamental grasses (17%), vegetables and herbs (14%), and perennial plants (7%).

Samples by host category: Trees and Shrubs 28%, Field Crops 16%, Turf and Orn. Grass 17%, Vegetables and Herbs 14%, Perennials 7%, Buildings and Grounds 5%, Small Fruits 6%, Annuals 2%, Tree Fruits 3%, Other 2%, Insect ID 1%, Humans 0%, Water body 0%, Animals 0%

Finally, before we get to diagnoses, below are the “Top 40 Hosts” (actually 42 because of ties) submitted in 2023. Note that 101 plant genera were received only once last year. Note: “Home and Garden” and “Arthropod ID” overlap, with some additional overlap with dwellings.

Top 42 host plants submitted: Tobacco 198, Tomato 153, Boxwood 125, Strawberry 105, Cucurbits 105, Soybean 103, Household 82, Home and Garden 51, Hollies 48, Oaks 45, Crucifers (veg. & field crops) 45, Wheat 38, Fir 37, Arborvitae 35, Corn 30, Insect/Arthropod ID 29, Maple 28, Azalea/Rhododendron 26, Apple 25, Pepper 24, Redbud 23, Dogwood 23, Sweetpotato 22, Magnolia 22, Ligustrum 21, Rose 21, Blueberry 21, Grape 21, Blackberry 18, Leyland Cypress 18, Potato 17, Hosta 17, Camellia 16, Crape Myrtle 16, Ornamental cherry/plum 16, Lettuce 15, Peach 14, Hydrangea 14, Chrysanthemum 13, Commercial Building 13, Cotton 13, Juniper 13


Below are summaries of the most common diagnoses for our most common hosts.

Tobacco was the most commonly submitted plant for diagnosis, comprising a little more than 8% of all of our samples. Most samples where no pathogen was found resulted from our testing of cured tobacco for blue mold (Peronospora hyoscyami f.sp. tabacina)  — thus it’s good we didn’t find any! Phytophthora nicotianae was very common, as were RhizoctoniaAlternaria, and Pythium. We diagnosed tobacco with the thrips-transmitted Tomato Spotted Wilt Virus (TSWV) fourteen times, which was prevalent last year as well.

Top diagnsoes for tobacco in 2023: No pathogen found 51, Phytophthora 33, Rhizoctonia 28, Alternaria 20, Pythium 17, Ralstonia 16, Erwinia 14, TSWV 14, Abiotic disorder 12, Cercospora 10, Fusarium 6

Tomatoes were the second most commonly submitted plants in 2023 and, as such, numerous pests and pathogens were found in this host. Abiotic and other disorders were the most commonly identified issues. Beyond that were several plant pathogens, including TSWV, Fusarium, Pseudomonas, Stemphylium and Alternaria.

Top tomato diagnoses in 2023: Abiotic disorder 29, Incomplete submission 25, No pathogen/no pest or disease of concern 19, TSWV 11, Fusarium 9, Pseudomonas 9, Stemphylium 9, Alternaria 7, Ralstonia 6

Boxwoods (Buxus spp.) were commonly sent in to the clinic, many for identification of the destructive disease boxwood blight (Calonectria pseudonaviculata). Nematodes were the most common diagnosis followed by several diseases. Typical boxwood arthropod pests (mites and leafminers) were also identified from boxwoods multiple times. Some issues were either abiotic in nature, or we were unable to identify the cause of the problem due to lack of sufficiently good samples.

Top boxwood diagnoses in 2023: Nematodes 62, Phytophthora 38, Pseudonectria (Volutella) 31, Incomplete submission 19, Abiotic disorder 18, Calonectria (boxwood blight) 14, Colletotrichum 13, Eurytetranychus 11, Monarthropalpus 8

Strawberries suffered from numerous diseases, most commonly BotrytisNeopestalotiopsis, Fusarium, and Pythium. As for arthropods, spider mites made the list (not surprising), but cyclamen mites (Phytonemus pallidus), were only diagnosed once.

Top diagnoses for strawberry in 2023: Botrytis 35, Neopestalotiopsis 32, Fusarium 28, Pythium 28, Rhizoctonia 18, Colletotrichum 16, Abiotic disorder 13, Phytophthora 12, Family Tetranychidae 6, Gnomonia 6, No pathogen found 6

Cucurbits also appeared to suffer from more abiotic disorders than disease or arthropod pests. Potyvirus (transmitted by aphids) was the most prevalent disease diagnosis, followed by Fusarium in cucurbits.

Top diagnoses for cucurbits in 2023: No pathogen/pest of concern 21, Potyvirus 17, Abiotic disorder 12, Fusarium 11, Incomplete submission 9, Stagonosporopsis 9, Rhizoctonia 7, Powdery mildews 4, Didymella 3

Finally, in soybeans the clinic diagnosed several diseases most commonly, including Fusarium, Cercospora, and Soybean vein necrosis virus (SVNV). Nematodes were also very often diagnosed from this host.

Top diagnoses for soybean in 2023: Fusarium 39, Cercospora 26, Nematodes 21, Soybean Vein Necrosis Virus (SVNV) 19, Diaporthe 14, Abiotic disorder 11, Colletotrichum 10, Dectes 10, Rhizoctonia 10, Macrophomina 8, Pythium 7

Notable Finds

Every year the clinic identifies organisms that are new, either to the country or state, or represent a significant host shift or record. The following are some of the notable organisms we identified in 2023:

Pest/Pathogen Host First Report: NC* New Pest/Host Combination**
allium leafminer (Phytomyza gymnostoma) Allium spp. (garlic, onion, leeks) X
Herbaspirillum (likely H. huttiense) elephant ear (Alocasia) X
cercosporoid fungus (Thedgonia ligustrina) ligustrum (Ligustrum sinense) X
powdery mildew (Podosphaera physocarpi) ninebark (Physocarpus) X
cercosporoid fungus (Pseudocercospora physostegiae) false dragonhead (Physostegia virginiana) X
bacterial leaf scorch (Xylella fastidiosa) elms (Ulmus spp.) X
vascular streak dieback (VSD) sassafras (Sassafras) X
black root rot (Berkeleyomyces basicola) Fothergilla  X
fungus (Embellisia sp.) garlic (Allium sativum) X
Cucumber mosaic virus (CMV) habanero pepper (Capsicum chinense) X
anthracnose (Colletotrichum sp.) celery (Apium graveolens dulce) X
Impatiens necrotic spot virus (INSV) tomato (Solanum lycopersicum) X
powdery mildew (Erysiphe diffusa) curry leaf tree (Bergera koenigii) X
powdery mildew (Podosphaera xanthii) garden balsam (Impatiens balsamina) X

*species may have been present in the state already, but this was the first official diagnosis
**only significant new pest/host combinations for the state

allium leafminer maggot (Phytomyza gymnostoma) in garlic

allium leafminer (Phytomyza gymnostoma) in garlic

Herbaspirillum bacterium (likely H. huttiense) in elephant ear (Alocasia)

Herbaspirillum (likely H. huttiense) in elephant ear (Alocasia)

cercosporoid fungus (Thedgonia ligustrina) in ligustrum (Ligustrum sinense)

cercosporoid fungus (Thedgonia ligustrina) in ligustrum (Ligustrum sinense)

powdery mildew (Podosphaera physocarpi) on ninebark (Physocarpus)

powdery mildew (Podosphaera physocarpi) on ninebark (Physocarpus)

cercosporoid fungus (Pseudocercospora physostegiae) on false dragonhead (Physostegia virginiana)

cercosporoid fungus (Pseudocercospora physostegiae) on false dragonhead (Physostegia virginiana)

bacterial leaf scorch (Xylella fastidiosa) on elm (Ulmus spp.)

bacterial leaf scorch (Xylella fastidiosa) on elm (Ulmus spp.)

vascular streak dieback (VSD) on sassafras (Sassafras)

vascular streak dieback (VSD) on sassafras (Sassafras)

Black root rot (Berkeleyomyces basicola) on Fothergilla 

black root rot (Berkeleyomyces basicola) on Fothergilla

Embellisia fungus on garlic (Allium sativum)

Embellisia fungus on garlic (Allium sativum)

Cucumber mosaic virus (CMV) on habanero pepper (Capsicum chinense)

Cucumber mosaic virus (CMV) on habanero pepper (Capsicum chinense)

anthracnose (Colletotrichum sp.) on celery (Apium graveolens dulce)

anthracnose (Colletotrichum sp.) on celery (Apium graveolens dulce)

Impatiens necrotic spot virus (INSV) on tomato (Solanum lycopersicum)

Impatiens necrotic spot virus (INSV) on tomato (Solanum lycopersicum)

powdery mildew (Erysiphe diffusa) on curry leaf tree (Bergera koenigii)

powdery mildew (Erysiphe diffusa) on curry leaf tree (Bergera koenigii)

powdery mildew (Podosphaera xanthii) on garden balsam (Impatiens balsamina)

powdery mildew (Podosphaera xanthii) on garden balsam (Impatiens balsamina)

Other Highlights

In 2023 we welcomed a new member to the lab: Dr. Cora McGehee! Cora hit the ground running, making numerous diagnoses and quickly getting familiar with the lab and working with clients and samples.

Matt Bertone and the clinic were highlighted in the May issue of Our State, North Carolina’s largest magazine. This issue included several stories about extension and it was an honor to be among those articles!

Photos from Our State article "The Bug Man of Raleigh"

Besides performing diagnoses, lab members gave numerous extension talks and webinars. Mike Munster and Matt Bertone continued to provide updates on arthropods and diseases for the Plants, Pests and Pathogens webinar series for extension master gardener volunteers (EMGVs).

We informally record the most “common” things we see (anecdotally), and in 2023 for arthropods it appeared to be a big year for the following: bald-faced hornets (Dolichovespula maculata), stag beetles (Lucanidae), Japanese beetles (Popillia japonica), green June beetles (Cotinis nitida), larger elm leaf beetles (Monocesta coryli) and late season large caterpillar defoliators (especially oakworms, Anisota spp.). Cora McGehee mentioned she thought that Potyviruses (on cucurbits) and TSWV (on tomatoes) were very common, while Mike Munster says it was a record bad year for boxwoods in home landscapes. Swarna Moparthi mentioned that strawberries with Neopestalotiopsis were noticeably common as was Soybean vein necrosis virus (SVNV) in soybeans.

Lab Publications

Chase, K. D., Graney, L., Ainslie, Z., & Bertone, M. A. (2023). Labena grallator (Say) (Hymenoptera: Ichneumonidae) Found Associated with the Non-Native Callidiellum rufipenne (Motschulsky) (Coleoptera: Cerambycidae). Proceedings of the Entomological Society of Washington, Vol. 125, pp. 187–189. https://doi.org/10.4289/0013-8797.125.1.187

Kirchner, M., Bertone, M., Blaimer, B. B., & Youngsteadt, E. (2023). Colony Structure and Redescription of Males in the Rarely Collected Arboreal Ant, Aphaenogaster Mariae Forel (Hymenoptera: Formicidae). Proceedings of the Entomological Society of Washington, Vol. 125, pp. 77–88. https://doi.org/10.4289/0013-8797.125.1.77

Oten, Kelly LF, Eric Day, Theresa Dellinger, Heather Harmon Disque, Lawrence E. Barringer, Jessica Cancelliere, Liam Somers, and Matthew A. Bertone. “First records of elm zigzag sawfly (Hymenoptera: Argidae) in the United States.” Journal of Integrated Pest Management, 14, no. 1 (2023): 12. https://doi.org/10.1093/jipm/pmad009

Bertone, M. (2023). Manual of Afrotropical Diptera, Volume 3: Brachycera–Cyclorrhapha, excluding Calyptratae. American Entomologist. https://doi.org/10.1093/ae/tmad071

Bertone, Matthew A., Kelly L. F. Oten, Emmeline J. Redick, Abigail R. Ratcliff “Notes on Larvae of the Rarely-Collected Wood Gnat Genus Olbiogaster Osten Sacken (Diptera: Anisopodidae),” Proceedings of the Entomological Society of Washington, 124(4), 873-876, (14 July 2023)

Moparthi, S., Johnson, A., and Braun, U. 2023. Podosphaera cerasi- An old foe of sweet cherry with a new name –its biology, epidemiology, and beyond. Journal of Plant Pathology. DOI: doi.org/10.1007/s42161-023-01354-9

Moparthi, S., Jailani A.A.K, and Braun, U. 2023. First record of Erysiphe diffusa causing powdery mildew on Bergera koenigii in the USA. British Society for Plant Pathology. DOI: 10.1002/ndr2.12175

Bradshaw, M. Boufford, D., Braun, U., Castlebury, L., Dominick, S., Moparthi, S., Jennings, K., Maust A., Pandey, B., Slack, S., Pfister, D. 2023. An in-depth evaluation of powdery mildew hosts reveals one of the world’s most common and widespread fungal plant pathogens. Plant Disease. DOI: 10.1094/PDIS-07-23-1471-RE

Moparthi, S., and Kleczewski, N. 2023. First report of curvularia leaf spot on Zea mays caused by Curvularia lunata in North Carolina. Plant Disease. DOI: doi.org/10.1094/PDIS-10-22-2306-PDN

Moparthi, S., Parikh, L.P., Troth, E.E.G., and Burrows, M. E. 2023. Identification and prevalence of seed-borne Botrytis spp. in pulses of Montana. Plant Disease. DOI: doi.org/10.1094/PDIS-05-22-1236-RE

Bradshaw, M. Aime, C., Maust A., Moparthi, S., Jennings, K., Pane, A., Hendrix, D., Pandey, B., Rokas, A., Yuanning, L., Pfister, D. 2023. Extensive intragenomic variation in the internal transcribed spacer (ITS) region, the universal barcode in kingdom fungi. iScience. 10.1016/j.isci.2023.107317


The PDIC received numerous samples in 2023, resulting in thousands of diagnoses that helped homeowners, growers, researchers, and other clients identify plant problems and arthropods. Many of these diagnoses lead directly to timely and accurate management recommendations. Samples also helped agricultural extension agents and extension master gardener volunteers (EMGVs) learn to diagnose issues for themselves, by verifying the culprits (or bystanders).

Finally, we are very grateful to have so many collaborators and specialists who aid us in diagnosing related plant issues. There are too many to name individually, but we appreciate the help from members of NC State Horticultural Science, Crop and Soil Sciences, Plant and Microbial Biology, as well as specialists from the North Carolina Department of Agriculture and Consumer Services and other organizations.

We look forward to serving you in 2024!

Links to reviews from previous years: