Tuesday, June 25, 2024

Plant Diseases

by Tricia Harris

by Tricia Harris, Helmsley Walled Garden

I spotted a nasty looking red orange mark on some of the leaves of the cordon pears on the east wall as I was walking round the garden the other day.

I picked a leaf and turned it over. To my horror there appeared to be a growth of raised pustules of such ugliness on the underside of the leaf I strongly suspected that aliens were taking over the pears.

Happily for me, the explanation was far more mundane. It was pear rust, a fungal infection for which there is no treatment other than picking off the infected leaves and either burning them or disposing of them in household waste. The fungal spores are not killed by composting so popping them in the compost bin will only spread the problem further.

In truth I should have recognised it for what it was sooner. The red orange mark was certainly indicative of rust but the height and spread of the pustules caught me on the hop as I hadn’t seen anything that big before.

Sadly it would appear that fungal infections like rust, mildews and cankers are on the rise due to the changes we are seeing in our climate. I’ve noticed that a lot of our phlox have got powdery mildew this year.

This will be due to the incredibly dry soil and root conditions they have borne with this summer. This has meant we have had to water them, creating moist and humid conditions around the leaves: perfect conditions for powdery mildew to thrive.

The phlox in question are part of a trial we are conducting in conjunction with the magazine Gardening Which? Looking at such aspects their vigour, susceptibility to disease, length of flowering period and floriferousness we’ll inspect them each week and feed the results back to Which over a three year period.

Powdery mildew is not the fault of the poor Phlox, it’s always been a martyr to it. What’s made it worse for these little ones is that they were newly planted earlier in the year at the start of the trial and the weather has been particularly hard to new plants this year.

I’m very big on giving things a really good water when they are planted and then not mollycoddling them. Water if it stays really dry but otherwise, they must get used to their surroundings, their bedfellows and the rain. Not a philosophy I could practise this summer. Let’s just say this year I spent a lot of time out with a watering can.

With rust and mildews, there are no treatments so good plant hygiene is the order of the day. Remove infected leaves and burn or dispose of anywhere but the compost heap. Try and get any leaf litter off the soil as well as it simply harbours the fungal spores and sets them free to do their worst the following spring.

I’ll be on patrol round the pears ready to pick off any new infected leaves, do say hello if you see me.

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