Pear trellis rust has made its way into Leslie Cox’s garden.

What’s that on my pear tree leaves?

Pear trellis rust a 'new-ish' fungus to the Island

Leslie Cox

Special to The Record

Sometimes it takes the slap of a wet leaf to get your attention. Well, mine anyways.

Truthfully, I was concentrating more on keeping one eye on John, who was up on the roof cleaning out gutters, and the other on picking pears while balanced where I should not have been – the top step of the short step-ladder. (I only did that twice but was definitely tempting fate.)

Safety nudge acknowledged and back to the wet leaf.

Even through smeared glasses, the red-orange spot stood out brilliantly a few inches from my nose. What the heck? Pear leaves are not that colour in the fall.

Flipping the leaf over, I discovered a really weird growth directly underneath the red-orange spot. Now I was seriously perturbed.

Turns out this thing is pear trellis rust, or Gymnosporangium sabinae for the Latin lovers. Originally native solely to Europe, I read it was positively identified on pear trees in Victoria back in 1961. Probably introduced through importation of infected ornamental junipers and it has spread from there.

It is a heteroecious fungus, meaning it needs two plant hosts to complete its life cycle, pear and juniper. It overwinters on the juniper tree in a dormant state and feasts on the pear tree from roughly May to August or September.

The recommended isolation distance between the two species is 305 metres to keep the fungus at bay. However, the fungus spores are known to travel as far as 10 km in the wind, so how to protect our pear tree which is exposed to prevailing winds across open fields?

Thankfully, this fungus is a biotroph. It only lives on living material, so is unlikely to actually kill the tree. There were also relatively few leaves with red-orange spots on the top side and weird growths underneath this year.

Best recommendation is to prune the overwintering galls from junipers before April and to remove pear leaves with ugly growths before August. (Easily spotted because of the red-orange circle on top side.)

For more information on pear trellis rust, and photos, go to my website at www.duchessofdirt.ca.

 

 

Leslie Cox co-owns Growing Concern Cottage Garden in Black Creek. Her website is at www.duchessofdirt.ca and her column appears every second Thursday in the Record.

 

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