Taking an environmentally sensitive approach to pest management


Missouri Environment & Garden


Josephine Mgbechi-Ezeri
University of Missouri
Plant Science & Technology
(573) 882-3019

Plant Diagnostic Clinic 2018 annual report for horticultural crops

Josephine Mgbechi-Ezeri
University of Missouri
(573) 882-3019

Published: February 28, 2019

Sample diagnosis

In 2018, the MU PDC received a total of 426 samples which includes physical samples, walk-in samples (samples not charged) and digital images submitted by email for plant disease diagnosis, insect, weed and plant identification. Disease diagnosis accounted for 81% of the total sample processed and the month of June marked the peak of submission with 95 samples (Figure 1). Samples submitted to the clinic were categorized into different crop types such as field crops, turf, ornamentals, vegetables and fruits. Ornamentals were the largest sample category with 138, followed by field crops (79) and turf (74) (Figure 2).

Figure 1 Percentage distribution of samples submitted to the clinic by type of diagnosis

Figure 2 Distribution of samples submitted for disease diagnosis by sample category

Diseases diagnosed on Ornamentals

Winter injury, chemical injury and heat stress were the major issues diagnosed on ornamental plants in 2018. The extreme heat condition in Missouri in the past year left many trees with leaf scorching, a symptom similar with to bacterial leaf scorch, a disease caused by the bacteria Xylella fastidiosa. Despite the excessive drought, some disease issues such as anthracnose, the aforementioned bacterial leaf scorch, powdery mildew, canker and dieback were observed.

Table 1 A list of diseases and pests diagnosed on different ornamental plants in 2018

Common Name



Arborvitae Environmental stress Abiotic disorder
Ash Hole in bark Unidentified wood boring insect
Azalea Dieback Unknown cause
Leaf spot Unidentified fungus
Black Mondo grass Anthracnose Colletotrichum cereale
Boxwood Boxwood volutella blight Volutella buxi
Environmental stress Abiotic disorder
Winter injury Abiotic disorder
Bradford Pear Leaf spot Unknown cause
Carex Flacca Anthracnose Colletotrichum spp.
Rhizoctonia root rot Rhizoctonia spp.
Chicory No pathogen found Identification analysis
China Aster Unknown Unidentified fungus
Choke Cherry Lace bug Corythucha spp.
Juniper Environmental stress Abiotic disorder
Twig blight Botryosphaeria spp.
Crabapple Frogeye leaf spot Botryosphaeria obtusa
Dahlia Unknown Unidentified agent
Daylily Bacterial soft rot Pectobacterium spp.
Dogwood No pathogen found Identification analysis
Dragon Wing Begonia Heat stress Abiotic disorder
Dusty Miller Verticillium wilt Verticillium spp.
Eastern White pine Abiotic disorder Abiotic disorder
White pine decline Abiotic Factors
Winter injury Abiotic disorder
Eunonymus Shrub Twig blight Botryosphaeria spp.
Environmental stress Abiotic disorder
European Beech No pathogen found Identification analysis
European Hornbeam Cytospora canker Cytospora spp.
Canker Nectria spp.
Insufficient sample Identification analysis
Forsythia Dieback Unknown cause
Fragrant Sumac Anthracnose Colletotrichum spp.
Fringe Tree No pathogen found Identification analysis
Hawthorn Cedar-quince rust Gymnosporangium clavipes
Hosta No pathogen found Identification analysis
Hydrangea Pythium root rot Pythium spp.
Holly Twig blight Botryosphaeria spp.
No pathogen found Identification analysis
Abnormal root development Unidentified agent
Maple Anthracnose Kabatiella spp.
Insect damage Unidentified Insect
Environmental stress Abiotic disorder
Tar spot Rhytisma spp.
Japanese lilac Spider mites Tetranychidae
Japanese yew Heat stress Abiotic disorder
Winter injury Abiotic disorder
Environmental stress Abiotic disorder
Lavender Anthracnose stem blight Colletotrichum spp.
Lily-of-the-valley Leaf spot Unknown cause
Magnolia Chemical injury Abiotic disorder
Winter injury Abiotic disorder
Sooty mold Capnodium spp.
Spruce Abiotic disorder Abiotic disorder
Phomopsis twig blight Diaporthe occulta
Abnormal plant growth Abiotic disorder
Winter injury Abiotic disorder
Orchard grass Anthracnose Colletotrichum spp.
Oak Tree Insect damage Unidentified wood boring insect
Bacterial leaf scorch Xylella fastidiosa
Herbicide injury Abiotic disorder
Leaf spot Tubakia spp.
Oak decline Abiotic Factors
Powdery mildew Erysiphe spp.
Drought stress Abiotic disorder
Anthracnose Apiognomonia spp.
Canker Hypoxylon spp.
Oak leaf Phylloxeran Phylloxera glabra
Oak lace bug Corythucha arcuata
Oak twig canker and dieback Botryosphaeria quercuum
Privet Chemical injury Abiotic disorder
Insect damage Unidentified insect
Purple leaf Plum No pathogen found Identification analysis
Snapdragon Verticillium wilt Verticillium spp.
Sedum Bacterial blight Unidentified bacteria
Swedish Ivy Bacterial blight Xanthomonas spp.

Turfgrass disease diagnosis

Of the 74 turfgrass samples submitted for analysis, 37 were out-of-state from Iowa, Kansas, Kentucky and Illinois. Turfgrass species submitted for diagnosis include creeping bentgrass, fescue, zoysia and Kentucky bluegrass. Most samples were from creeping bentgrass putting greens, which like other cool season species endured a difficult spring with the 2nd coldest April on record followed by the warmest May – June on record. This weather anomaly, and resultant lack of spring, didn't allow for adequate root development prior to the summer stress period. On tall fescue lawns, several instances of gray leaf spot were observed in the St Louis and Columbia area. Gray leaf spot occurs late season (August – September), and has not been typical in recent years. The disease can be problematic since it can spread very quickly by spores, fungicide resistant populations are known, and management practices differ from brown patch, a more regular disease issue on tall fescue.

Table 2 A list of diseases and abiotic issues diagnosed on turfgrass in 2018

Type of turfgrass


Pathogen/abiotic issue

Bentgrass Environmental stress Abiotic
Algae Algae
Anthracnose basal rot Colletotrichum spp.
Basal leaf anthracnose Colletotrichum spp.
Black layer Abiotic
Lance nematode Hoplolaimus spp.
Pythium root rot Pythium spp.
Take-all Gaeumannomyces spp.
Winter desiccation Abiotic
Bacterial etiolation Bacteria
Fescue Anthracnose Colletotrichum spp.
Brown patch Rhizoctonia spp.
Gray leaf spot Pyricularia grisea
Melting out Drechslera spp.
Root-knot nematode Meloidogyne graminis
Zoysia Winter injury Abiotic
Chinch bug Blissus spp.
Large patch Rhizoctonia solani AG2-2 LP
Creeping bentgrass Black layer Abiotic
Fairy ring Various fungi
Pythium root rot Pythium spp.
Wet wilt Abiotic

Diseases diagnosed on fruits and vegetables

Fruits and vegetables submitted to the clinic were diagnosed with several issues like abiotic stress, chemical injury and diseases. Chemical injury reported on okra, tomato and potato in some cases occurred from herbicide used in close proximity or herbicide carryover in manure/compost. Foliar and fruit rot diseases were diagnosed on pumpkin, cucumber, cabbage, pepper and tomato. Root rot disease caused by Fusarium and Phytophthora species were reported on tomato, watermelon, blueberry and raspberry samples.

Table 3 A list of diseases and abiotic issues diagnosed on fruits and vegetables in 2018




Watermelon Crown, root and stem rot Phytophthora spp.
Two-spotted spider mite Tetranychus urticae
Tomato Herbicide injury Abiotic disorder
Abnormal plant growth Abiotic disorder
Bacterial leaf spot Xanthomonas spp.
Crown and root rot Phytophthora spp.
Early blight Alternaria solani
Fusarium wilt Fusarium oxysporum f.sp. lycopersici
Septoria leaf spot Septoria lycopersici
Pumpkin Fusarium fruit rot Fusarium spp.
Squash bug Anasa tristis
Potato Herbicide injury Abiotic disorder
Pepper Alternaria fruit rot Alternaria spp.
Bacterial soft rot Pectobacterium spp.
Cucumber Anthracnose Colletotrichum orbiculare
Cabbage Bacterial soft rot Pectobacterium spp.
Cantaloupe Cercospora leaf spot Cercospora spp.
Okra Chemical injury Abiotic disorder
Blackberry Dieback Unidentified fungus
Blueberry Bacterial leaf scorch Xylella fastidiosa
Botrytis blight Botrytis spp.
Crown and root rot Phytophthora spp.
Dieback Unknown
Stem canker Botryosphaeria spp.
Elderberry Leaf blight Alternaria spp.
Grape Fruit spot Unidentified agent
Peach Mold Penicillium spp.
Pear Canker Unidentified agent
Fire blight Erwinia amylovora
Raspberry Root rot Phytophthora spp.
Sphaerulina leaf spot Sphaerulina spp.
Apple Alternaria fruit rot and spot Alternaria spp.
Apple black rot Diplodia seriata
Fruit rot Unidentified agent
Bitter pit Abiotic disorder
Senescent breakdown Abiotic disorder
Lenticel breakdown Abiotic Disorder

The PDC is open year round for sample submission. A general diagnosis is $15, additional services are $10 each if special testing such as an ELISA/immunostrip, culture plating or molecular diagnosis is required. Please visit our PDC website http:// plantclinic.missouri.edu/ or call (573-882-3019) for more information.

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REVISED: February 21, 2017