Issue 12, September 22, 2021

August 2021 Plant Clinic Sample Summary

Summary of ornamental, fruit, and vegetable samples diagnosed August 2021.

The Plant Clinic remains open. We are currently operating with reduced staff and are only in the lab as needed for diagnostics and other lab work. We may not be able to answer or return phone calls in a timely manner though we are making every attempt to do so. You can also email us at

Samples shipped via USPS, UPS, and FedEx are all arriving in a timely manner. We recommend shipping early in the week (Monday-Wednesday) and keeping the tracking number so we can trace the package if needed.

We are receiving more maple and oak samples. A bur oak sample from Lake Co. tested positive for Oak Wilt (, a lethal oak disease. As a reminder, do not prune oak trees during the growing season!

We are seeing an increased number of oak samples with various insect pests, including kermes scale and jumping oak gall. While jumping oak gall is usually not considered a threat to overall healthy trees, heavy infestations especially on white oaks can cause browning and defoliation:

We’ve had a number of ornamental samples submitted displaying pot-bound roots. These plants were planted into landscape beds but the rootball does not appear to have been separated or opened up before planting. These plants did not establish well into the landscape and once the hot, dry weather started their poor root system was unable to take up sufficient water and the plants began to suffer. This is a good reminder to disrupt root balls when planting, everything from woody perennials to herbaceous annuals!

We’re also starting to see environmental scorch symptoms and symptoms characteristic of bacterial leaf scorch. We will be testing for bacterial leaf scorch later in the season (September and October). Samples can be submitted now and will be stored until we begin tests. For more information about bacterial leaf scorch, please see:

Host Pathogens and/or Pests Confirmed (C) or Suspected (S)
Arborvitae Phyllosticta needle blight (C), Phytophthora root rot (C)
Blackberry Cane and leaf rust (C), spider mites (C)
Boxwood Volutella blight (C), Boxwood leafminer (C), Boxwood spidermite (S), Boxwood psyllid (C), Environmental stress (S)
Catalpa Anthracnose (C), Verticillium wilt (C)
Chrysanthemum Fusarium canker (S), Fusarium wilt (S)
Crabapple Fungal cankers (C), Environmental stress (S)
Cucurbits (pumpkin, squash) Anthracnose (C), Angular leaf spot (C), Environmental stress (S)
Dahlia Dickeya stem rot (S)
Dogwood Mulberry whitefly (C), Transplant shock (S)
Garlic Acarid mites (C)
Juniper Kabatina needle blight (C)
Maple Anthracnose (C), Phyllosticta leaf spot (C), Oystershell scale (C), Maple spider mite (C), Maple spindle gall mite (C), Fungal cankers (C), Lecanium scale (C), Bark/Ambrosia beetles (S), Environmental stress (S)
Oak Oak wilt (C), Anthracnose (C), Leaf blister (C), Cristulariella leaf spot (C), Kermes scale (C), Jumping oak gall (C), Oak twig canker (C), Oak lace bug (C), Fugal cankers (C), Anthracnose (C), Environmental stress (S)
Pear Entomosporium leaf spot (C)
Pine Diplodia tip blight (C), Pestalotiopsis needle blight (C), Pine needle scale (C), Dothistroma needle blight (C), Environmental stress (S)
Privet Rhizoctonia root rot (C)
Raspberry Spur and Cane blight (C), Environmental stress (S)
Rudbeckia Verticillium wilt (C)
Serviceberry Environmental stress (S)
Spirea Cylindrosporium leaf spot (C)
Spruce Sudden Needle Drop (SNEED) (C), Pine needle scale (C), Rhizosphaera needle cast (C), Stigmina needle cast (C), Spruce spider mite (C), Sirococcus needle blight (C), Environmental stress (S)
Sunflower Alternaria leaf spot (C)
Tomato Cercospora leaf spot (C), Rhizoctonia crown and root rot (C)
Turf Rhizoctonia crown and root rot (C), Anthracnose (C), Dense thatch layer (C)

Diane Plewa

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