Issue 6, July 1, 2020

University of Illinois Plant Clinic Summary of ornamental, fruit, and vegetable samples received June 2020

It’s no surprise that our sample numbers are lower than usual this year. While the Plant Clinic remains open, we are currently operating with staff in the lab only as needed for diagnostics. We are often not able to answer or return phone calls in a timely manner. If you need to contact us, we suggest emailing for the fastest response.

Packages shipped via USPS are being picked up 3-4 times a week. FedEx packages are picked up as packages arrive, and UPS is delivering packages daily. No matter how you send a sample, we highly recommend keeping your tracking number and checking to see if the sample was delivered. If you notice that the package wasn’t able to be delivered (a delivery attempt or delivery failure), please contact us with the tracking number and the method used to ship the sample – we may be able to track it down locally.

Oak and Maple samples were the most common submissions, along with arborvitae, spruce, and, you guessed it, boxwood! We’re still seeing the usual needle blights and needle casts on fir, spruce, and arborvitae, along with fungal foliar diseases and fungal cankers on the maples and oaks. We haven’t confirmed Verticillium wilt or Oak wilt on any samples so far this year, but we’re waiting on a few very suspicious samples to finish growing in culture and I wouldn’t be surprised if we have positives for both diseases in July. We did confirm boxwood blight on one sample from a nursery.


Pathogens and/or Pests Confirmed (C) or Suspected (S)


Phyllosticta needle blight (C). Pestalotiopsis needle blight (C), Phomopsis dieback (C), Spruce spider mite (S), environmental stress (S)

Oak (bur, white, and black)

Oak leaf blister (C), Anthracnose (C), Callirhytis oak gall wasp (C), fungal cankers (C), environmental stress (S)

Spruce, Colorado Blue

Rhizosphaera needle cast (C), Stigmina needle blight (C), environmental stress (S)


Volutella blight (C), Fusarium canker (C), Macrophoma leaf spot (C), Boxwood leafminer (C), Boxwood psyllid (C), Boxwood spidermite (S), environmental stress (S)

Euonymus (Burning Bush)

Oedema (C), environmental or chemical stress (S)


Septoria leaf spot (C), fourlined plant bug (S)


Root rot (S)


Anthracnose (C), Leaf blister (C), environmental stress – windburn (S)


Diplodia tip blight (C)


Dothistroma needle blight (C), Diplodia tip blight (C), spider mites (S)


Leaf blotch (C)


Anthracnose (C)


Pythium root rot (C)


Fungal canker (C)

Diane Plewa

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