turns sneaky silver
HOPE you can solve this problem for me. I have floribunda roses
down my drive in a bark garden. They are probably about 12 years
old. They get VIP treatment - they're watered every week, sprayed
every two weeks, manured when necessary and dead-headed all the
time - but now they are getting silver blight.
I lost one rose three
years ago and replaced the dirt where it had been growing. Despite
this, 'Aotearoa' and 'Eldorado' are now blight-stricken.
When I prune it is always
fine and I spray them on the same day. It appears if I want to grow
roses down the drive I am going to have to remove all the dirt before
I can plant any more.
Can you tell me why
my roses are getting silver blight? My roses out the back of the
house are doing fine. I hope you can tell me what I am doing wrong.
SOUNDS like the problem is silver leaf disease (Chondrostereum
purpureum), a fungal disease which gets in through broken branches
or pruning wounds. The first sign of the disease is when leaves
on a branch or even on the whole plant turn silvery. It's a relatively
common disease in peach or nectarine trees but can also affect apples,
pears and even poplars and willows, as well as roses. Perhaps the
infection is coming from trees in your garden or nearby.
no easy cure. Changing the soil won't help as the infection is airborne.
Badly infected plants usually go into a slow decline. Rose expert
Doug Bone suggests pruning out the infected shoots as soon as you
see them, cutting back hard to take out the whole branch with the
silvered leaves. Doug also reports success using Trichodowels. You
insert these into a hole drilled in the base of the affected rose
bush, but unfortunately they are now only available in commercial
quantities for orchardists.
To reduce the risk of
infection, prune your roses and other susceptible trees only on
warm sunny days when there has been no rain for at least the previous
24 hours. Sterilise your tools after each plant, by dipping the
blades in methylated spirits before wiping them clean or wipe them
with a cloth soaked in meths.
Gardener, Issue 141, 2004, Page 22
Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.