Massive leaf-loss on Pyracantha

[Chas Caunt]

I have a Pyracantha (sorry, don't know the variety) growing against an
East-facing wall. Apart from being a bit 'leggy' because of it's shady
position, it seems to have been quite happy there, growing to about 8
feet high and 10 feet across.

For the past few years, in late spring/early summer, it has suffered
with some loss of new leaves. This year it has become much worse and I
don't know whether it is caused by disease, pest, growing environment
or something I have (or haven't) done.

After a VERY large and vigorous flush of new leaves in spring, the
problem starts in early/mid May. Each of the affected leaves develops a
bronze-brown patch (it eventually darkens to a chestnut brown), usually
at the tip but sometimes at the base or leaf margin. The sides of the
leaf will then curl up until it has rolled into a tube. When it finally
falls off, the leaf is as dry and crisp as if it had been toasted.

I reckon that about 75% of this year's new leaves have been affected
leaving the shrub looking very threadbare. The older leaves are largely
unaffected by this, but the tops of some of them are covered with a
silvery film. If this film is removed, it reveals a black, sooty
substance. I just mention it in case it has anything to do with the
larger problem.

The border that the shrub grows in is covered with a weed-suppressing
sheet and about an inch depth of gravel.

Sorry for the long-winded description, but I am desparate to find and
treat the cause.

Thanks in anticipation

Chas Caunt

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[Jo Moulder]

Dear Chas
I have had exactly the same problem. I have fan trained Pyracanthas growing
against the north side of a fence , some of it gets afternoon sun and the
arches of it above the fence get full sun . My problem follows your
description exactly .I reckon 75% of my new growth was affected. I think
the silvery coating you described on the old leaves is the result of a
leaf boring caterpillar and the silver bit is the top membrane of the leaf
and i think the black mould stuff is it poo. I had a massive attack of this
creature last year. I think the loss of young leaves this year may be due
to fire blight, and am going to read up on it, mine looked gorgeous one day
, flush with new growth and now looks positively scraggy .

Regards Jo ~:c)

[Nick Maclaren]

While fireblight is possible, my experience is that my pyracantha
doesn't get it, even when an immediately adjacent chaenomeles is hit
very hard. If you catch fireblight in time (and you have to be VERY
fast), spraying with Bordeaux mixture seems to work.

Regards,
Nick Maclaren,
University of Cambridge Computing Service,
New Museums Site, Pembroke Street, Cambridge CB2 3QG, England.
Email: nm...@cam.ac.uk
Tel.: +44 1223 334761 Fax: +44 1223 334679