Overview of 2025 Horticultural Submissions

In 2025, the MU Plant Diagnostic Clinic (MU-PDC) received a total of 443 samples specifically within the horticultural categories (Ornamentals, Fruits, and Vegetables). These diagnostic requests represented 66.72% of the clinic's total annual volume, highlighting the strong continued reliance of Missouri's home gardeners and commercial horticulture and landscape industries on our services.

Following the trend of previous years, the months of August and September saw the highest volume of submissions, accounting for approximately 43% of the horticultural samples for the entire year. This peak corresponds with late-season plant stress and the visible progression of foliar diseases in woody ornamentals.

Sample Sources and Client Demographics

Table 1 The distribution of sample sources of horticultural samples in 2024.

^*Note: Percentages based on horticultural total; some categories may overlap with field crop sources.

Distribution of Horticultural Samples by Category

Figure 1 Distribution of samples submitted for disease diagnosis by sample type (Field crops not included)

Field Crops remained the dominant category for diagnostic services in 2025, followed by various ornamental and fruit categories:

As the chart indicates, woody ornamentals remained the largest individual category within horticulture, followed by fruit and vegetable diagnostics. In the category of Woody Ornamentals, combined deciduous and evergreen categories accounted for 214 samples. Deciduous samples peaked in September (39), largely driven by various Oak species (Pin Oak, Post Oak). In 2025, MU Extension in partnership with the Missouri Department of Conservation, continued to offer free testing for all common oak tree diseases.

Summary of Ornamental Plant Diagnosis

Deciduous trees were the primary source of ornamental submissions. Oak species dominated this category, with Pin Oak (34) and Post Oak (22) being the most frequent hosts. Diagnostics often centered around late-season diseases such as Oak wilt (19), Bacterial Leaf Scorch (11) and Tubakia leaf spot (8).

Evergreen samples remained steady throughout the year, with pine tree and arborvitae being common hosts. Many of these cases were diagnosed as abiotic stress, including winter injury and drought stress, which were exacerbated by the variable weather patterns seen early in the 2025 season.

Summary of Fruit and Vegetable Diagnosis

The 2025 season presented unique challenges for specialty crop producers:

Vegetables

• Tomato (43) remains the most frequently submitted vegetable sample.
• Common issues included early blight, Septoria leaf spot, bacterial canker and suspected herbicide damage (Dicamba/2,4-D), particularly in samples submitted by home gardeners.

Fruit and Small Fruit

• Small Fruit: Grape (56) samples accounted for most of this category, with a significant diagnostic spike in October due to a research project focusing on new virus/viroid detection on grapes in Missouri. In addition to the viruses detected from Missouri Elderberry Virus survey funded by U.S. Department of Agriculture’s (USDA) Agricultural Marketing Service through grant AM22SCBPMO1152 (Specialty Crop Block Grant Program by MDA), a few new viruses such as Cherry Leafroll Virus (CLRV), Elderberry Virus A (EVA) and Elderberry Virus B (EVB) were detected from the samples from Missouri and Wisconsin.
• Fruit: Six Watermelon were tested positive for oomycete diseases like Phytophthora and Pythium root rots following wet spring conditions.

Submission and Clinical Improvements

To assist in providing timely results, MU-PDC has streamlined our online digital submission system. We encourage all horticultural 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

Table 2. Major Diseases and Issues in Horticultural Crops (2025).