PLEASE find enclosed a leaf from my pear tree. Would you please identify the problem as this is the second year that my tree has had this rust-looking disease?

R WESTWOOD

REG SAYS:

WELL, you have identified it yourself in the last sentence, as it is pear rust, a once quite uncommon disease in Britain although it is more widespread all over the rest of Europe. You note that I said “once uncommon” as I now come across it much more often at Gardeners’ Questions evenings.

The symptoms consist of reddish spots which appear on the top of the leaves, gradually darkening and often displaying brighter edges.

Rough brown areas appear under the foliage and these make the airborne spores that fly off to infect its alternate host Juniperus Sabina.

When the spores get a hold on the conifer they create spindle-shaped swellings on the stem which then release more airborne spores in spring that can fly for about three miles in order to re-infect pears again. So you see this is one of the more interesting fungal diseases as it requires two hosts to complete its full life cycle.

I should also mention that with pears the fungus can also sometimes infect young stems or even the fruit.

So what can we do about it? Well if you have any Juniperus Sabina varieties in your garden you could dig them out, but of course the disease can fly for several miles so spores could still arrive from elsewhere easily enough.

Although you will not find the diseases mentioned on fungicide packs in the garden centre, any fungicide suitable for use against pear scab or powdery mildew will also give you some rust control too.

However, I think that Bayer Dithane 945 will probably give the best control. Apply it regularly after the foliage has totally expanded in spring, as you would for scab.

Finally, collect up all the fallen leaves and dispose of them in the autumn and remove any infected leaves whenever you spot them.

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Write to Reg Moule Gardeners’ Questions, Editorial, Worcester News, Hylton Road, Worcester WR2 5JX. No correspondence can be entered into. Reg Moule answers your questions courtesy of David’s Nurseries, Martin Hussingtree.