Clinic Update: Early Fall Samples Submitted to Diagnostic Clinic

Sample numbers submitted to the diagnostic clinic have begun to decrease. The majority of samples received in recent weeks have been from trees and shrubs and many of the problems have been related to the severe heat and drought experienced this summer.

We have had oak samples with sawfly and other insect feeding damage to the foliage, as well as various galls on the foliage and branches. A chlorotic red maple was found to be Mn deficient, while other maples were submitted with a leaf scorch attributed to the drought. Several arborvitae samples have been submitted with environmental damage, usually large branches or the entire plant turning brown and dieing. We have had a number of juniper samples with similar symptoms. We have had a number of spruce samples with needles turning purple or brown and falling from the tree. In some cases, the needles are still green but have suddenly fallen. In some cases there is evidence of past mite infestation, but we have not seen any disease causing pathogens associated with these plants and suspect that hot dry conditions have stressed these trees. We have had a few white pine samples with typical white pine decline symptoms, one of these tested positive for Phytophthora root rot. The weather earlier this summer was very stressful to plants, and some seem to have continued to decline with rainfall and more moderate temperatures. In some cases plants may have been over-irrigated this summer, or are in poorly drained locations that have been affected by more recent heavy rainfall events. It is also important to keep in mind that many of these plants are not suffering from foliar diseases that can be identified from a few leaves or a small branch, and a larger sample may be necessary. Contact the diagnostic clinic if you are unsure how much material to submit.

We have seen fewer fruit and vegetable samples. We have received a number of pumpkins that tested positive for Phytophthora fruit rot and a watermelon with bacterial fruit blotch.

We have received a few turf samples. While Rhizoctonia was found in one of the samples, diseases have not been present in others. Some of these samples are from exposed areas that were not irrigated during hot dry weather and did not recover well, particularly on poor soils. Areas with Poa trivialis have resulted in dead patches where this grass has not recovered well with more favorable weather conditions.

We have received a few insect submissions, including the drugstore beetle, Stegobium paniceum, and rice moth, Corcyra cephalonica. Most of our weed submissions have not been from horticultural areas, however mugwort, Artemisia vulgaris is a problem particularly when introduced with new nursery stock, and jack-in-the-pulpit Arisaema triphyllum seed heads are very conspicuous right now and have resulted in a number of submissions.

We look forward to receiving your samples. Please refer to the sample submission section of our website or contact us for more information on sample submission.

Simeon Wright and Sandra Davis
Plant Diagnostic Clinic
573-882-3019