Clinic Update: Early Summer samples Submitted to the Plant Diagnostic Clinic

As often occurs during early summer in Missouri the humidity is high and temperatures are climbing. Many plants develop problems as a result. The following is a recap of some of the samples that were submitted to the clinic in June.

Herbicide injury on a tomato plant. Photo by Simeon Wright.

Ornamental sample submissions have included impatiens and chrysanthemums with Rhizoctonia stem rot, as well as chrysanthemums with Pythium root rot. We have had several turf sample submissions including samples with slime mold and sooty mold, as well as Rhizoctonia sheath spot and brown patch.

As gardens begin to produce, vegetable samples increase for the clinic. We have received several tomato samples with Fusarium wilt, as well as bacterial leaf spot, Septoria leaf spot and walnut wilt, which can be confused with Fusarium wilt with similar vascular discoloration within affected stems. A lab isolation can help to identify the presence of Fusarium in suspect samples growing near walnut trees. Walnut trees can create symptoms in many plants including tomato, potato, alfalfa, and other herbaceous and woody plants when juglone produced by walnut and related trees causes wilting and eventual death in early to mid-summer. Plants growing further away may not die, but show signs of being stunted. Among other vegetable submissions, a potato sample was submitted with common scab symptoms and a watermelon sample was submitted with Fusarium wilt. Other fruit sample submissions include grapes with anthracnose and grape phylloxera, and apple with cedar apple rust.

Tree samples are common submissions to the clinic. Several have been tested for oak wilt with negative results so far. There are other problems that can cause decline and mortality in oaks, some of the pin oaks submitted have had severe iron chlorosis, which can lead to branch dieback when severe. Fire blight submissions continue to come in on ornamental pear and apple. Several spruce submissions have been submitted with spider mites, Cytospora canker and Stigmina needlecast. Samples with aphids and ash flower gall have also been submitted.

Ash flower gall. Photo by Simeon Wright.

A common submission to the clinic this spring and early summer has been herbicide injury issues, usually due to accidental drift from nearby applications. Some applications can drift long distances to affect certain plants that are particularly sensitive. This year a number of samples have been submitted, especially from tomato and grape. It is important to keep in mind with these submissions that it is important to have fresh samples as soon as the injury is observed.

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 and Sandy Davis
Plant Diagnostic Clinic
573-882-3019