#plant pathogen

[wildflowers-of-southern-ontario]

Black Tar Spot Rhytisma acerinum Rhytismataceae

It is a fungus that commonly affects sycamores and maples, like in the above photographs. Fortunately it does not have adverse effects on the trees in the long term, but it is still a little unsightly.

Photographs taken on October 13, 2020, along the Etobicoke Creek Trail, Mississauga, Ontario, Canada.

[lazyevaluationranch]

29/2/2020

There is a cherry tree down the road a ways that has been infected by Psuedomonas syringae. This bacteria makes ice nucleation-active proteins, which have little slots for water molecules to fit into tidily. This makes the water freeze more easily, because it's already perfectly lined up to be ice crystals. Water inside the tree freezes, which splits the wood and bleeds sap to give the tree vaguely unsettling curled amber horns.

Psuedomonas syringae also floats up from trees into the atmosphere and freezes water up there. It grows hailstones. You know, Chunks of Ice that Fall Out of the Sky and Smash Things.

Two days ago, we brought home a couple of cherry trees to add to the orchard. Today we got some hail.

Scientists claim there’s no reason to conclude the Tawny-Horned Hailstone Tree sent us a warning that we'd better treat our new cherry trees right, or else. 

But everyone who’s ever farmed cherries knows better.

[microcosmicobservations]

Rust fungi can be terrible agriculturally but are fascinating nonetheless. This is Gymnosporangium sp. growing on juneberry fruits. All species of Gymnosporangium have two hosts where their life cycles are divided. The primary host is the juniper tree, where it fruits and produces spores to infect the secondary host - in this case, a juneberry tree. The white parts are spore tubes, and the orange dust is the spores.

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[aphidcluster]

Leaf spot disease symptoms on Fiber Hemp (Cannabis sativa).

[lovecraftsgarden]

Exobasidium rhododendri growing on Rhododendron hirsutum, the Hairy Alpenrose.

(via)

[drhoz]

#1239 - Miyagia pseudosphaeria - Sonchus Rust

And then, tonight, as I was getting these photos together to post on my blog, I noticed that many of the Sowthistle leaves had little yellow pimples on them, surrounded by dark pinkish rings - it soon figured out that it’s a another specialist, the Sonchus Rust Fungus (Miyagia pseudosphaeria).

The fungus was first noticed in Australia 20 years ago or so, but has no real effect at controlling the weed. Nor are the aphids, and their predator has its own problems, in the form of the wasp. True, it all reaches a balance eventually, but that balance is an invasive weed occupying habitat better reserved for Australian native plants, if you can find any that will survive beside driveways.

[aphidcluster]

Powdery mildew fungus (Phyllactinia fraxini) producing chasmothecia on European ash (Fraxinus excelcior).

[lovecraftsgarden]

Exobasidium vaccinii

Azalea with leaf gall caused by this fungus.

(via)