2022 Plant Disease and Insect Clinic Year in Review

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OK I know it’s March, so I am going to blame a warm early season this year for our delay getting this done. Better late than never, I guess!
Regardless, in total the Plant Disease and Insect Clinic and Turf Diagnostic Lab received 2,927 sample submissions in 2022, only a slight increase (4%) over the previous year. Excluding the turf, ornamental grasses, and sedges, the number is 2,477, a very slight increase (2%) over 2021. Of those, 2416 (98%) came from within the state of North Carolina. Most were samples for diagnosis, but 36 were tobacco for blue mold screening.
Note that most of these summaries do not include turf samples. For a summary of 2022 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 346. Here are the counties that submitted the most samples:

Bar graph showing the counties with the most number of samples submitted for 2022. Wake = 346, Buncombe = 123, Orange = 114, Henderson = 92, Durham = 55, Guilford = 54, Mecklenburg = 48, Granville = 47, Forsyth = 46, Person = 43, Rockingham = 43, Sampson = 42, Nash = 40, Wilson = 40, Wayne = 38, Brunswick = 37, Moore = 37

As expected, the summer months were the busiest, with the lab receiving more than 300 samples in both June and August. At 373 samples total, June averaged around 17 samples per day!

Bar graph showing number of samples per month for 2022. January = 92, February = 99, March = 225, April = 207, May = 252, June = 373, July = 293, August = 341, September = 289, October = 150, November = 92, December = 64

Samples can consist of images only, physical samples only, or a combination of both. In 2022, most samples were physical only (43%), closely followed by image-only samples (34%), then a combination of both (23%). This is similar to what we saw with 2021 samples.

Pie chart showing percentage of sample types submitted in 2022. Types are image only, physical only, or both

These samples were submitted by different types of clients. Although direct submissions by clients made up 34% of all submissions, the remaining samples were submitted by state agricultural extension agents, various consultants, or a combination of them. Again, the breakdown is very similar to 2021 numbers.

Pie chart showing percentage of samples by contact type submitted in 2022. Types are client alone = 34%, NCCE agent = 40%, consultant = 22%, both agent and consultant = 4%

The majority of samples (including those for turf) came from home grounds (31%), followed by crops in the field (20%), greenhouses (13%), golf courses (11%), households (6%), and container nurseries (4%; tied with commercial grounds).

Pie chart showing percentage of sample by host site type submitted in 2022. Types are home grounds = 31%, field crops = 20%, greenhouse = 13%, golf course = 11%, household = 6%, container nursery = 4%, commercial grounds = 4%, field grown nursery = 2%

The most common types of hosts submitted were trees and shrubs (26%), followed by field crops (17%), turf and ornamental grasses (15%), vegetables and herbs (15%), and perennial plants (7%). Interestingly, field crops and vegetables/herbs swapped ranks from 2021. We are not sure yet where the increase came from, but we will be investigating this trend.

Pie chart showing percentage of samples by host type submitted in 2022. Types are trees and shrubs = 26%, field crops = 17%, turf and ornamental grasses = 15%, vegetables and herbs = 15%, perennials = 7%, Buildings and grounds = 6%, small fruits = 4%, annuals = 3%

Finally, before we get to diagnoses, below are the “Top 40 Hosts” submitted in 2022. Note that 126 plant genera were received only once during 2022. Also there was a steep drop in hemp samples, going from 20 in 2021 to four in 2022. Note: “Home and Garden” and “Arthropod ID” overlap, with some additional overlap with dwellings.

Table showing top 40 hosts submitted to the clinic in 2022. Tobacco 241 Corn 30 Tomato 172 Caneberries 25 Cucurbits (watermelon, cucumber, squash, pumpkin, cantaloupe) 104 Redbud 21 Soybean 102 Petunia 21 Dwelling 97 Camellia 20 Boxwood 85 Hickory and Pecan 19 Strawberry 68 Juniper 19 Home and Garden 56 Magnolia 19 Cole crops (incl. radish) 46 Grape 18 Azalea and Rhododendron 45 Dogwood 17 Maple 43 Apple and Crabapple 16 Hollies 42 Bean 16 Cherry, plum, and peach (ornamental and for fruit) 42 Pine 16 Arthropod ID 42 Rose 16 Peppers 40 Cotton 13 Oaks 38 Human 13 Arborvitae 35 Crape myrtle 13 Sweetpotato 34 Blueberry 13 Wheat 32 Leyland Cypress 13 Fir 30 Fungus ID Request 13


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

Tobacco was the most commonly submitted plant for diagnosis, comprising close to 10% of all of our samples! Granville wilt (Ralstonia) and black shank (Phytophthora nicotianae) were very common, as were Alternaria and bacterial soft rot/ stalk rot. We even diagnosed tobacco with the thrips-transmitted Tomato Spotted Wilt Virus (TSWV), which was prevalent this year in many hosts and not diagnosed from tobacco in a few years.

Bar graph showing top diagnoses for tobacco. Granville wilt 59 Black shank 57 Alternaria 47 No pathogen or pest found 40 Bacterial soft rot 36 Cercospora 26 Rhizoctonia 15 TSWV 13

Tomatoes were the second most commonly submitted plants in 2022 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, Southern bacterial wilt (Ralstonia), and others. Tomato Yellow Leaf Curl Virus (TYLCV), transmitted by whiteflies (Bemisia), was more common than in other years.
Bar graph showing most frequent diagnoses for tomatoes in 2022. No pathogen found 45 Southern bacterial wilt 25 Tomato spotted wilt 23 Oedema; Edema 19 Other abiotic disorders 17 Unidentified Agent 11 Insufficient sample or info 9 Early blight 8 Begomovirus, incl. TYLCV 7 Spider mites 7

Strawberries suffered from numerous abiotic disorders, but on the disease side Botrytis and Colletotrichum were the most prevalent organisms found, as well as some Phytophthora and Pythium. As for arthropods, spider mites made the list (not surprising), but despite requests to check for cyclamen mites (Phytonemus pallidus), they were only diagnosed a few times (though in high densities sometimes).

Bar graph showing most frequent diagnoses for strawberries in 2022. Abiotic disorder 22 Botrytis 12 Colletotrichum 8 Spider mites 8 Xanthomonas 7 Phytophthora 6 Pythium 6 Fusarium 5 Neopestalotiopsis 5

Cucurbits also appeared to suffer from more abiotic disorders than disease or arthropod pests. The “mildews” (both downy and powdery) were the most common diseases found, while spider mites and thrips were the common arthropod pests of cucurbits.

Bar graph showing most frequent diagnoses for cucurbits in 2022. No pathogen found 46 Unidentified Agent 10 Downy mildew 8 Thrips 7 Abiotic disorder 6 Insufficient sample 5 Powdery mildew 5 Spider mites 5

Finally, declining boxwoods (Buxus spp.) were commonly sent in to the clinic, many for identification of the destructive disease boxwood blight (Calonectria pseudonaviculata). There was state-wide, active screening of samples for this disease as well. Most commonly, several diseases, nematodes, and typical boxwood arthropod pests (mites and leafminers) were identified from boxwoods. 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.

Bar graph showing most frequent diagnoses for boxwoods in 2022. Nematodes 24 Abiotic disorder 19 Insufficient sample 16 No pathogen found 15 Volutella blight 15 Boxwood mite 11 Unidentified Agent 10 Boxwood blight 9 Boxwood dieback/canker 9 Boxwood leafminer 8 Phytophthora 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 2022:

Pest/Pathogen Host First Report: NC New Pest/Host Combination
elm zigzag sawfly (Aproceros leucopoda) American elm (Ulmus americana) X
Japanese holly fern mottle virus (JHFMoV) Japanese holly fern (Cyrtomium falcatum ‘Rockfordianum’) X
Urocystis trillium (smut) Trillium sp. X
Alternaria celosiicola (leaf spot) Celosia cristata ‘Armor Orange’ X
Plasmopara cercidis (downy mildew) redbud (Cercis canadensis) X
Pseudomonas asplenii (bacterial blight) Birds Nest Victoria Fern (Asplenium nidus ‘Victoria’) X
Rosellinia necatrix (root rot) American beautyberry (Callicarpa americana) X
Sawadaea polyfida (powdery mildew) Japanese maple (Acer palmatum) X
Xanthomonas axonopodis pv. citri (citrus canker) Lime (Citrus limetta) X
Curvularia lunata (Curvularia leaf spot) corn (Zea mays) X
Gnomoniopsis smithogilvyi chestnut (Castanea dentata) X
Coniella granati (fruit rot) pomegranate (Punica granatum) X
Drechslera sp./spp. hemp (Cannabis sativa) X
Neopestalotiopsis saprophytica Japanese Persimmon (Diospyros kaki) X
A green caterpillar-like larva of a sawfly feeding on an elm leaf

Larva of the elm zigzag sawfly (Aproceros leucopoda), a new pest for NC. For information on this species, please see our fact sheet. Photo by Matt Bertone

Rosellinia necatrix root rot on American beautyberry (Callicarpa americana).

Rosellinia necatrix root rot on American beautyberry (Callicarpa americana). Photos by Mike Munster

Powdery mildew (Sawadaea polyfida) on Japanese maple (Acer palmatum).

Powdery mildew (Sawadaea polyfida) on Japanese maple (Acer palmatum). Photos by Mike Munster

Downy mildew (Plasmopara cercidis) on redbud (Cercis canadensis)

Downy mildew (Plasmopara cercidis) on redbud (Cercis canadensis). Photos by Mike Munster

Drechslera sp./spp. on hemp (Cannabis sativa)

Drechslera sp./spp. on hemp (Cannabis sativa). Photos by Swarna Moparthi

Fruit rot (Coniella granati) on pomegranate (Punica granatum)

Fruit rot (Coniella granati) on pomegranate (Punica granatum). Photo by Swarna Moparthi

Other Highlights

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).

With help from collaborating specialists, the lab also planned and lead the 2022 Plant Problem Diagnostics Short Course for the Central Region of NC. During this week-long event, 19 extension agents from across the region gathered to look at diseases and pests out in the field, then attended sessions in the lab to help them build their diagnostic skills. Based on evaluations of the course, it was a great success! We hope to do more of these workshops in the future.

NC Agricultural Extension Agents wandering around a corn plot looking for pests and pathogens at the Piedmont Research Station (Salisbury, NC).

NC Agricultural Extension Agents wandering around a corn plot looking for pests and pathogens at the Piedmont Research Station (Salisbury, NC).

NC Agricultural Extension Agents looking for pests and pathogens of ornamentals at J.C. Raulston Arboretum (Raleigh, NC)

NC Agricultural Extension Agents looking for pests and pathogens of ornamentals at the J.C. Raulston Arboretum (Raleigh, NC)

Photo showing agents watching a talk about arthropods in a lab setting

NC Agricultural Extension Agents attending a laboratory session on identifying common arthropods on NC State University main campus (Raleigh, NC). Photo by Tracy Blake

One other major effort was the development of an online decision guide for submitting samples of various “cypresses”. These plants, especially arborvitae and Leyland cypress, are common in landscapes and have numerous problems, many of which are not caused by pests or diseases. This effort was made so that agents and clients could better identify these problems, and make informed decisions on whether and how to submit samples to the clinic. The guide provides key identifying characters and has photos of the symptoms being described. We hope it’s valuable to a broad audience!

Screenshot of one of the couplets in the new cypress decision guide.

An example of one of the identification couplets in the Cypress Decision Guide.

Lab Publications

Bertone, M.A., K.L.F. Oten, E.J. Redick, and A.R. Ratcliff. Notes on larvae of the rarely collected wood gnat genus Olbiogaster (Diptera: Anisopodidae). Proceedings of the Entomological Society of Washington. (in press)

Chetverikov, P.E., and M.A. Bertone. (2022) First Rhyncaphytoptine Mite (Eriophyoidea, Diptilomiopidae) Parasitizing American Hazelnut (Corylus Americana): Molecular Identification, Confocal Microscopy, and Phylogenetic Position. Experimental and Applied Acarology.

Efromson, J., R. Lawrie, T.J.J. Doman, M. Bertone, A. Bègue, M. Harfouche, D. Reisig, R.M. Roe. (2022) Species Identification of Caterpillar Eggs by Machine Learning Using a Convolutional Neural Network and Gigapixel Microscope. Agriculture, 12(9), 1440.

Gagné, R. J., and M.A. Bertone. (2022) Redescription of Dentifibula viburni (Felt) (Diptera: Cecidomyiidae) and review of the genus. Zootaxa. 5175 (5): 583–592.

Skvarla, M.J., Bertone, M.A., and Liesch, P.J. (2022) Murder Hornet Mayhem: The Impact of the 2020 Giant Hornet Panic and COVID-19 Pandemic on Arthropod Identification Laboratories. American Entomologist. Volume 68, Issue 2, Summer 2022, Pages 38–43,

Bertone, M. A., Gibson, J. C., Seago, A. E., Yoshida, T., & Smith, A. A. (2022). A Novel Power-Amplified Jumping Behavior in Larval Beetles (Coleoptera: Laemophloeidae). PLOS ONE 17(1): e0256509.

Moparthi, S., Kleczewski, N. 2023. First report of curvularia leaf spot on Zea mays caused by Curvularia lunata in North Carolina. Plant Disease.

Moparthi, S., Parikh, L.P., Troth, E.E.G., and Burrows, M. E. 2022. Identification and prevalence of seed-borne Botrytis spp. in pulses of Montana. Plant Disease.

Bradshaw, M., Quijada., Tobin, P.C., Braun, U., Newlander, C., Potterfield, T., Alford, E.R., Contrearas, C., Coombes, A., Moparthi, S., Buchholz, E., Murphy, D., Enos, W., Fields- Tyalor, A., Bower, A., and Pfister, D. H. 2022. More than just plants: Botanical gardens as a source of fungal diversity. HortScience.

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. Accepted in the Journal of Plant Pathology.

Common Pantry Pests and their Management. S. Crawley & M. Bertone. 2022 NC State University Extension Publication

Elm Zigzag Sawfly. K oten & M. Bertone. 2022 NC State University Extension Publication – Invasive Forest Pests


The PDIC received numerous samples in 2022, 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 2023!

Links to reviews from previous years: