Extension Plant Diagnostic Clinic Report

The Plant Diagnostic Clinic is part of the Soil Testing and Plant Diagnostic Service Laboratories at the University of Missouri and handles samples submitted for disease, insect, and weed identifications, as well as management recommendations. Most clinic operations are handled by clinic staff, however other Division of Plant Science Agronomy, Entomology, Horticulture, and Plant Microbiology and Pathology extension faculty handle insect and weed identification and assist when needed. The 2006 growing season represented an increase in sample submissions over the past few years. Most samples were submitted through the mail while some were personally delivered to the clinic. A few digital photos were also submitted by email. Samples were submitted from 81 Missouri counties with 20 percent of the submissions from Boone County. Nearly 90 percent of the samples were received between May and September.

In 2006, woody ornamentals represented a majority of samples submitted to the clinic. We also received a lot of field crop samples as well as fruit, turf, vegetable, herbaceous ornamental, and forage samples (Figure 1). The top 5 plants submitted to the clinic were soybean, tomato, pine, wheat, and spruce respectively. Among horticultural crops, tomato, pine, spruce, maple, and oak were the most popular submissions. Approximately 42 percent of the plant disease samples submitted to the diagnostic clinic were affected by abiotic (non-living) problems. We received a lot of samples this year with environmental problems related to the dry weather, beginning last spring with evergreen samples damaged from winter desiccation. As the season progressed, we saw a lot of leaf scorch problems in the clinic. However, a majority of samples were biotic plant disease problems (caused by living organisms) (Figure 2). In the spring, anthracnose was common on shade tree foliage. Root rot problems were common during the summer where ornamentals were over-watered. We also tested a lot of ornamentals for sudden oak death (Phytophthora ramorum) this year. Fortunately, none of the samples received by the clinic were positive for the pathogen. An additional 10 percent of plant disease submissions were diagnosed with insect problems. Many of these samples had spider mite injuries.

For many individual plant species, we did not receive enough samples to identify trends. However, large numbers of certain samples were received. Several bedding plants (petunia, impatiens, vinca etc.) and Chrysanthemum samples were affected by root and lower stem rots caused by Phytopthora, Pythium, Rhizoctonia, or a combination. Several turf samples were submitted with slime mold this year. Zoysia with large patch or chinch bug infestations was also common. Many of the tree problems were related to plant stress this year, especially the pine and spruce samples, beginning with winter desiccation samples in the spring and additional damage during hot dry weather. Common tomato samples included Fusarium wilt and herbicide injuries. Several pepper samples had bacterial leaf spot. We also received a number of grape samples with black rot or herbicide injuries symptoms.

We also received a number of insect and weed samples for identification this year. Carpenter ant, cigarette beetle, hackberry psyllid, and boxelder bug were the most common insect submissions. Weed submissions were quite varied, but several samples of switchgrass and bermudagrass were submitted for identification.

While we hope your plant problems are minimal in 2007, we are ready for any samples you wish to send and hope you will continue to use our services, or send us a sample when you run into plant problems if you have not done so in the past. The more samples we receive, the more information we have about the plant problems occurring in Missouri, which can be used to provide updates during the growing season. This information can help everyone protect and improve the health of their plantings.

Please see our website at http://soilplantlab.missouri.edu/plant/index.htm for more information about the plant diagnostic clinic and sample submission. You can also contact the lab at plantclinic@missouri.edu or 573-882-0623.

Thank you for your support of the diagnostic clinic.

Simeon Wright
Coordinator Plant Diagnostic Clinic