Plant Diagnostic Clinic 2018 annual report for horticultural crops

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

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

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

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.