Disease Digest

Peony Measles

Cultivate your own garden, said Voltaire at the end of Candide.  Looking homeward, I note that peony measles, first seen in mid-July has continued to develop.  Measles, or red spot or leaf blotch or Cladosporium leaf blotch disease are alternative names for this fungal disease. It is caused by, you guessed it, Cladosporium paeoniae or, who knew, with its new moniker, Dicholocladosporium chlorocephalum. 

 

  On the upper leaf surface, reddish and brownish “measles”-like spots develop earlier in summer, now coalescing into purple blotches...

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Jim Chatfield

Crepe Myrtles For Ohio

While in Maryland and Virginia recently our Extension Nursery Landscape and Turf Team of diagnosticians admired crepe myrtles (Lagerstroemia indica) in whites, reds, and lavenders.  Absolutely gorgeous trees for their flower displays and their attractive bark.
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Jim Chatfield

The Other Guignardia...

Joe Boggs wrote a great article “Guignardia Leaf Blotch Running Rampant” the other day, which caused me to reflect on another Guignardia fungus often ignored, but very important.  The other Guignardia, Guignardia bidwellii, is one responsible for causing the disease Black Rot of Grape.
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Erik Draper
Curtis E. Young

Guignardia Leaf Blotch Running Rampant

Our continual wet weather over much of Ohio this season has been a two-edged sword. On one hand, we haven't had to drag hoses to water our landscapes. On the other hand, a number of fungal plant pathogens that require wet conditions to infect and produce their associated diseases are running rampant. Such is obviously the case for Guignardia aesculi; the fungus responsible for Guignardia Leaf Blotch of Aesculus.
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Joe Boggs

Gallignostics

  Let us call this A Case of Gallignostics. Plant galls are defined as abnormal plant growths caused by a gall-maker; the gall-maker being certain insects, mites, fungi, and bacteria. From horned oak gall to bacterial crown gall, from maple bladder galls to cedar-apple rust galls, there are many galls of interest to horticulturists. Relative to all this, Joe Boggs recently got an e-mail from Michael Goldman of the Grange Insurance Audubon Center:

 

  I'm a big fan of the BYGL, and found something here that might be interesting for it.  The pictures I took look like some...

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Jim Chatfield
Joe Boggs
Oak Leaf Blister Disease chatfield.1 Sun, 07/02/2017 - 19:50

  Oak leaf blister, a fungal disease caused by Taphrina caerulescens, is widespread this year on a range of oak species, both in the white oak and red oak groups. Symptoms include raised, blistered, greenish-yellow spots on upper leaf surfaces and darker, corresponding sunken spots on lower leaf surfaces, though sometimes the raised and sunken aspects may be obscured. Fungal growth can sometimes be seen on undersurfaces of leaves.

 

...
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Jim Chatfield

Sycamore Anthracnose Symptoms Fade

  This morning I got a message from Frank Leon, horticulturist with Barnes Nursery, complete with the above image showing the thinning of sycamore (American planetree; Platanus occidentalis), a common sight seen in northwest Ohio this Spring. The problem is sycamore anthracnose, caused by the fungus Apiognomonia veneta.

 

 

  This particular anthracnose fungus occurs on planetrees, including our native sycamore, but less so on Platanus orientalis and the hybrid between these two planetrees, Londone planetree (PlatanusX acerifolia...

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Jim Chatfield
Yellow Polka Dotted... Tomatoes?? draper.15 Tue, 06/27/2017 - 20:16

I was called out to visit a high tunnel vegetable grower, who was concerned about what he was seeing on tomato leaves, which he hadn’t seen before on the plants.  He told me that spots had suddenly began to appear on his tomato plants, and that he really didn’t want to lose the plants or the huge crop of tomatoes that the plants had set.

 

...
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Erik Draper

Rosaceous Rusts Rampage

Rust on serviceberry? Yes. Has the whole world gone mad? No. It just reveals itself to each of us in manageable gulps.  We talk frequently of three “cedar rusts” on BYGL: cedar apple rust, cedar hawthorn rust, cedar quince rust, all caused by separate species in the fungal genus Gymnosporangium (bygl.osu.edu/node/781).  In fact, it is not as simple as this – there are over 40 species of the Gymnosporangium fungus. 

 

  Not only that, but there are over 480 species in 11 genera of the rose family (Rosaceae) that are affected by Gymnosporangium ...

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Jim Chatfield
Maple Anthracnose chatfield.1 Sat, 06/10/2017 - 23:55

Jeff Stachler, OSU Extensioneer in Auglaize County sent the following message this past Tuesday on June 6:

  “A maple tree in the front of a home yard has leaves with the symptoms you see in the photos.  Veins and leaf tips are black with yellow and brown colors below the black.  Is there anything that can be done or should be done?” He also sent the tell-tale photo above, showing “water-soaked” darkish lesions along leaf veins.

 

Right on time. Last June 5, I took a picture of a neighbor’s red maple in Doyletown in northeast Ohio of the same problem: maple...

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Jim Chatfield