General Discussion:

Black spot and powdery mildew on roses


Messages posted to thread:

From:Date:Zone:
24-Oct-00 11:37 PM EST   
25-Oct-00 02:24 PM EST   
Katherine25-Oct-00 02:36 PM EST   
Susan25-Oct-00 03:21 PM EST   
26-Oct-00 12:23 PM EST   
Chris26-Oct-00 12:32 PM EST   
Maria27-Oct-00 11:42 AM EST   
Gail27-Oct-00 11:42 PM EST   
Liza Ordubegian31-Oct-00 03:00 PM EST   
Susan01-Nov-00 07:28 PM EST   


Subject: Black spot and powdery mildew on roses
From:
Zone:
Date: 24-Oct-00 11:37 PM EST

Hello--I've had a terrible time this year with black spot and powdery mildew on my roses. Four of my bushes completed dropped their leaves real early. I've been removing the dead leaves from the garden--as not to leave anything on the ground to spread this problem. Can this be cured? Is there something I can spray on my roses first thing in the Spring to curtail this problem? I tried some ?? dusting powder, but I have way too many bushes to be treating this way. Any suggestions would be greatly appreciated.


Subject: RE: Black spot and powdery mildew on roses
From:
Zone:
Date: 25-Oct-00 02:24 PM EST

I spray my roses once a week with a formula of two tablespoons of Baking Soda and one tablespoon of liquid ivory hand soap which I add to two gallons of boiling water, mix, let cool and spray on your roses. This seems to control the powdery mildew. Stan


Subject: RE: Black spot and powdery mildew on roses
From: Katherine
Zone:
Date: 25-Oct-00 02:36 PM EST

This may be old news to you, but make sure to water in the morning, and only on the ground, not from above (keep the leaves dry). Also, you mention you have way too many bushes. Are they getting enough air circulation? You might want to thin the bushes out next spring so they have lots of space around them (1 to 2 feet). Good luck!


Subject: RE: Black spot and powdery mildew on roses
From: Susan
Zone:
Date: 25-Oct-00 03:21 PM EST

FYI, I tried the baking soda thing without any success - I was down to about three leaves per bush by early July when I decided to give up and go to a weekly spray of Safer's Defender. The bushes recovered quite well - they all got leaves again and came back into bloom and are still in bloom now. They still have visable Black Spot but are hanging in there.

I've just bought a biological, suposedly non-toxic to people, product called Rose Flora from Better Flora in the US. It looks like it's only available by mail order or via their web site (www.better-flora.com) It's supposed to be sprayed on the ground now to help kill off stuff that over-winters, but you need to spray weekly through the growing season too. I also bought the companion product called Wilt Pruf which is supposed to provide winter protection from dehydration for roses and broad-leafed evergreens like Rhododendrons and Pieris. Has anyone else tried this stuff? How effective do you think it is?

The Rose Flora came with an interesting article by a professor of rose genetics (?!), basically stating that the best route is to buy genetically resistant rose varieties and listing a large number of roses using his resistance categories. I bought the wrong roses! A variety with a similar name to my variety is highly resistant but mine is only moderately so! Maybe I'll rip them out next year and replace them with something more resistant - although not many of the roses on his list are in the White Rose or Sheridan catalogues, so maybe they're not hardy here. Their web site has the resistance lists on it if you're interested in looking at it.

Personally, I'm not convinced that roses are worth the effort at times. In my last garden we gave up on roses, in part because of Black Spot, but also because our Maple trees started shading them out. We just moved into this house last year, so I decided to try again - having a very wet summer was not the ideal conditions, so I'll probably give it another year before I decide whether to turf the pampered beauties out of the garden for good!


Subject: RE: Black spot and powdery mildew on roses
From:
Zone:
Date: 26-Oct-00 12:23 PM EST


Subject: RE: Black spot and powdery mildew on roses
From: Chris
Zone:
Date: 26-Oct-00 12:32 PM EST

Some roses are quite resistant to blackspot, e.g. the Explorer and probably also Parkland series, as well as many modern shrub roses - my 3 David Austins all came through this damp, cool summer with few problems. My neighbour's hybrid teas were defoliated, however. If your roses are prone to blackspot then regular spraying with fungicide may be the only really effective solution in a summer like the one just past.


Subject: RE: Black spot and powdery mildew on roses
From: Maria
Zone:
Date: 27-Oct-00 11:42 AM EST

Don't give up on roses! This was my first year of gardening, and I have 3 roses so far with no problem. They are the easiest and most enjoyed plants I have. Be sure to thin/prune them so they get air. I didn't thin my zinnias as I was so happy they were growing and blooming and had a horrific case of rapid powdery mildew. I learned my lesson. They need air as much as water, food. If I did get the leaves wet it was only in the morning on a sunny day so they could dry off. I read that garlic planted around them deters beatles, which I'll do myself next year. I saw one big one but wasn't sure if it was a good or bad beatle. RE: getting rid of roses - We have two Westerlands (apricot climbers)that I had came upon and had to wait months before spring came. I really wanted these. I didn't see how disease resistant etc they are. They are young, but they are nowhere near the beauty, strength, etc., of our other rose. So do I toss these two?? It's a hard decision and they weren't cheap. The best rose of the two is definitely the yellow Dream Rose my husband picked out. I have since found other disease resistant varieties. If it doesn't say, ask, and resist any temptation on ones that aren't and focus on ones that are. i don't let myself look. i'll see how the Westerlands do next year (such small blooms! so infrequent! it's not like the picture!) and may have to take them out to my dad's in the country.


Subject: RE: Black spot and powdery mildew on roses
From: Gail
Zone:
Date: 27-Oct-00 11:42 PM EST

I have quite a few roses in my garden - some hybrid teas and a few Austin roses. Depending on the weather, the hybrid teas can be quite susceptible to black spot (I live on the Wet Coast), but I never seem to have problems with the Austin roses. They grow in the same conditions as the others, but seem naturally more resistant. I do spray the teas with a baking soda, soap and garlic solution which helps but does not eliminate the fungus. I've also found that an early spring sulphur/dormant oil spray goes a long way towards preventing the problem too - but be certain to do it before any leaf growth. If I were to replan my garden now that I have a little more gardening experience, I would likely change the varieties of roses (teas at least) that I put in, but I certainly wouldn't quit growing them. Fragrant, home-grown roses take some beating ! Gail P.S. The Austin roses that I am growing are called 'Heritage' and 'Evelyn' - they look sensational all season long !


Subject: RE: Black spot and powdery mildew on roses
From: Liza Ordubegian
Zone:
Date: 31-Oct-00 03:00 PM EST

It seems the best defense is a good offense when it comes to roses. I have a climbing explorer, Henry Kelsey that stayed deep green with nary a spot. Another shrub rose, Carefree wonder, was indeed a wonder. It is still blooming away here in zone 6b. My climbing apricot beauty is suffering, but I will try some dormant oil in the spring. My Henry Hudson also is doing well and is blooming still, though not as prolifically as that Carefree wonder.


Subject: RE: Black spot and powdery mildew on roses
From: Susan
Zone:
Date: 01-Nov-00 07:28 PM EST

I do all the 'right' things re air circulation, pruning etc. I've got the roses surrounded by garlic chives and onion chives which are both supposed to be good deterents. My roses are Carefree Wonder and they are neither carefree or wonderous! Carefree Beauty is the highly resistant one - I picked up the wrong ones by accident! Looking at whether the variety is resistant or not from the nursery information is a chancy thing - I've seen varieties listed as very resistant in nursery information that are listed as very susceptible in non-nursery sources... So rose growing seems like a chancy/probable-to-be-chemical-dependant things. I find it interesting that Potentillas, which are members of the rose family, are so hardy and disease free while roses are so susceptible to everything. I've become quite a fan of Potentillas, especially the pink and the white ones. They looked so much better in my driveway boreder than the roses - they spill so gracefully over the curb and blossomed continuously from early June to mid-October. The jury's still out on whether the roses get turfed next year or not!


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