Clinic Update: Mid-Summer samples submitted to the Plant Diagnostic Clinic

Azalea with Phytophthora crown and root rot. Photo by Angel Ramsey

Vinca with aerial Phytophthora blight. Photo by Angel Ramsey

Fruit and vegetable samples submitted to the clinic included several tomatoes with Fusarium wilt, spider mite injury, walnut wilt and suspect TSWV (tomato spotted wilt virus). We also had potatoes with common scab and several pepper plants with bacterial leaf spot. Grapes were submitted with black rot, anthracnose and grape-berry moth. Blackberries were diagnosed with blackberry psyllid and sun scald and blueberries with leaf scorch. Peaches samples were submitted with brown rot.

Samples from trees make up a lot of the submissions to the clinic at any time of year. It is important to keep in mind that a sufficient sample for diagnosis would be branches that show symptoms but have not completely dried out and died. To test for certain diseases, we may need very specific sample material, you can always call us for more information on what to submit. This month tree samples have included a couple maples with dieback and decline. We have tested several oaks for oak wilt, but have not had any positives recently. When tested, suspect oak wilt samples may be negative when sample materials have become too hot in shipment, or simply because the fungus becomes less active in the branches during hot summer weather. A quince was diagnosed with cedar-quince rust. Other samples have included a juniper with a severe spider mite infestation, magnolia with scale, and a white pine with a root rot that was positive for Phytophthora using serological testing methods.

We have also had a lot of ornamental plant submissions. Many of these samples appear to be from plants that have been over-watered to compensate for heat and drought. It is important to check the irrigation to ensure it is functioning properly and to check the soil under mulch before watering to ensure that more water is needed. An azalea was submitted with a root and stem rot that tested positive for Phytophthora. A vinca sample submission had Phytophthora aerial blight. A chrysanthemum and several petunias were submitted to the clinic with Pythium root and stem rot. Other chrysanthemum sample submissions had Rhizoctonia stem rot and a Fusarium wilt. Hosta and sedum samples were infected with anthracnose. Finally, a lantana sample was diagnosed with Rhizoctonia stem rot.

As always, we look forward to receiving your samples in the clinic. While we are often not able to diagnose plant problems from a description of the problem over the phone, you can call us if you have questions about what material to submit for a quick and accurate diagnosis.

Simeon Wright, Sandye Davis and Angel Ramsey
Plant Diagnostic Clinic
573-882-3019