During the first half of 2026, the MU Plant Diagnostic Clinic (MU-PDC) processed a total of 420 physical samples and 129 digital diagnostic submissions. The physical diagnostic services comprised plant disease diagnoses (109), insect identifications (5), and plant/weed identifications (6). Compared to the same period in 2025, physical sample volume increased by 113%, while digital submissions rose by 150%.

Sample Sources and Client Demographics

Table 1 The distribution of sample sources (1/2026-6/2026).

Distribution of Samples by Category

Figure 1 Distribution of samples submitted for disease diagnosis by sample type (1/2026-6/2026)

Summary of Ornamental Plant Diagnosis

Figure 2 Number of deciduous and evergreen ornamental samples (1/2026-6/2026)

A total of 197 deciduous tree samples were received, and oak species dominated this category. Among these oak tree samples, 127 were used for a research project focusing on white oak mortality in Missouri. Beginning in June, MU Extension in partnership with the Missouri Department of Conservation, continued to offer free testing for all common oak tree diseases. MU-PDC will continue studying prevalence of oak diseases across the state, including Tubakia Leaf Spot, Bacterial Leaf Scorch and Oak Wilt. So far, the clinic has received 45 samples, 7 samples were confirmed with Oak Wilt and 2 samples were confirmed with Bacterial Leaf Scorch. Due to the extended period of wet and cool weather conditions in the first half of 2026, we have seen increasing numbers of fungal foliar diseases such as anthracnose, rust and leaf spot/blight diseases on deciduous trees. Fungicide applications are not recommended currently since most of these foliar diseases are seasonal, and disease pressure typically declines with the onset of summer conditions. Cultural practices such as improvement of irrigation in the summer and sanitation by removing the diseased and dead branches and leaves, as well as chemical applications in early spring next year will help control these diseases.

It was a challenging spring for many evergreen ornamental trees across the state. The total sample submissions for species such as arborvitae, white pine, spruce, and cedar doubled compared to previous years. Diagnostic analysis revealed that the majority of dieback and needle blight cases were abiotic, meaning they were primarily caused by environmental conditions rather than living pests or pathogens. Missouri experienced one of its driest winters on record in 2025, placing severe drought stress on these trees and leaving them highly vulnerable to secondary pests and opportunistic pathogens. Combined with drastic temperature swings in early spring, trees gradually began exhibiting widespread dieback symptoms. As summer heat intensifies, proper irrigation will be crucial to keeping stressed evergreens alive and recovering.

Summary of Fruit and Vegetable Diagnosis

Figure 3 Symptoms of Tomato Spotted Wilt Virus: Tomato leaves turn bronzing and chlorotic with dark necrotic spots.

Tomato (21 samples) remains the most frequently submitted one among 35 vegetable samples. Diseases diagnosed include Fusarium wilt, Tomato Spotted Wilt Virus, early blight, bacterial canker and suspected herbicide damage. Anthracnose disease was confirmed in several solanaceous and cucurbit vegetables probably due to the humid weather conditions.

Submission and Clinical Improvements

To assist in providing timely results, MU-PDC has streamlined online digital submission system. We encourage all clients to take clear, well-focused photos of both the overall plant environment and close-up symptoms before shipping physical material.

Contact Information

University of Missouri-Plant Diagnostic Clinic
28 Mumford Hall, Columbia, MO 65211
Phone: 573-882-3019
Email: plantclinic@missouri.edu
X (Twitter): x.com/MUplantclinic