Diagnostics: It's the Environment, Man

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Question # 12 of our 20 Questions of Plant Problem Diagnostics is: What Is The Environmental History?”.  Here are three quick examples of the importance of this question.


Planetree Perserverance.  As predicted in bygl node.1305 on June 11, planetrees, especially the more susceptible American planetree (sycamore, Platanus occidentalis) that looked almost leafless due to sycamore anthracnose in May and June throughout much of Ohio, have now largely re-foliated and look fine. Cool, moist conditions during leaf emergence, so key to disease development, are past history and trees recovered nicely.


Sycamore anthracnose in early June
Defoliation from sycamore anthracnose in early June


Recovery from sycamore anthracnose by mid-July
Recovery from sycamore anthracnose by mid-July


All Hail Honeylocust. Orange-yellow discoloration on stems, elliptical cracking on those stems. Are these fungal cankers on this backyard thornless honeylocust (Gleditsia triacanthos var. inermis ‘Imperial’) in Denver, Colorado? Not totally sure, but I suspect the smoking gun is the homeowner’s report of the environmental history of major hailstorms this spring and summer – and the “What Exactly Do You See/” question #6 of Plant Problem Diagnostics. What I exactly saw was the damage in question only occurring on – upper stem surfaces.


Hail damage on honeylocust
Presumed hail damage on honeylocust


Underside of honeylocust stems
Underside of honeylocust stem with no hail damage


Aesculus Avoidance. On a Denver street, a reminder of home – Ohio buckeye! Leaf scorch in the hot summer heat, and some insect feeding, but – whither the Guignardia  leaf blotch fungal diseases, common on the genus Aesculus (buckeyes and horsechestnuts) and the moderately susceptible Ohio buckeye (Aesculus glabra). No Guignardia. The absence of the environmental component of the disease triangle is the key here: not a lot of wet and humid conditions in spring in Denver.


Ohio buckeye with leaf scorch in Denver
Physiological leaf scorch on Ohio buckeye in Denver


Guignardia leaf blotch on Aesculus
Here is what Guignardia leaf blotch looks like on susceptible Aesculus in Ohio


Insect feeding on buckeye in Colorado
Insect feeding - or is it hail damage - on buckeye in Denver


Buckeye butterfly
And the buckeye butterfly in a greenhouse display at the Chatfield Farms area of the Denver Botanic Gardens


Young tattooist makes his mark
Denver flavor: A young tattooist makes his mark in a street mural


Einstein mural
Diagnostics: Question Everything!