Races of Blackspot

Are we contributing to the development of differing races of blackspot by spraying roses with fungicides…All this spraying should be expected to cause development of fungicide-resistant strains of blackspot…

I have seen blackspot on ‘Knock Out’ here, and I am not talking just one leaf on a bush.

Some leaves that remain on a ‘Knock Out’ bush, late autumn in Sydney:

Your lucky day George.

Looks like there’s plenty of room for improvement there in Sydney.

Dunno if I should throw this KO out, or use it in a “breeding program” LOL… I feel I wasted yet another $25 AUD…

There’s nothing clean in your area?

It is strange Robert,I agree… At least I can test for these things here with some degree of confidence in a “breeding programme”…So far I am breeding fungus more than anything else…LOL

The only spotless plants I have ever seen here, are on display at major retail nurseries, and staff at one of these have told me that these plants are grown in a separate climate inland, where they are also sprayed and fertilized +++, and brought here for display at the nursery, in peak condition, to boost sales at various high sales times (eg. next weekend Mothers Day etc)…

George wrote: “So far I am breeding fungus more than anything else.”

Thanks for the good laugh, George.

After taking a depressing look around my place yesterday… I think I’m breeding deer more than anything else.

I have seen KO being unloaded from trucks that were highly effected by black spot.

As far as us effecting the evolution of black spot. By spraying you are forcing the selection process. that is why every few years they have to change chemical or change the concentration. Plants have been doing the same thing since time began. But pest always find away to bug you. One example of forced evolution due to spraying is the Q whitefly. Be glad you don’t have this.

Maybe having nothing that is resistant is actually a blessing. Because it forces you to bred resistance that does not rely on one single gene. Resistance that relies on single gene expression is easily by passed.

I am pretty good at breeding plants that have their leaves covered in snow for the holidays. They think its Christmas all summer long!!!

Has there been any testing done on the number of races of blackspot KO has shown to be resistant to?

Rainbow Knock Out has major mildew issues even here.

Knock Out has remained clean here, but I still find it too homely to look at.

Double Knock Out is far more aesthetic, but I do wonder if it is more or less healthy. Double Pink Knock Out looks like pepto bismal lol. I may try it as a pollen parent on some red floribunda types.

Knock Out has remained clean here<<<<

Jadae, by this do you maan KO gets absolutely no blackspot in our climate, or do you mean it gets very minimal (eg. like 5% or less) blackpot in your climate?

CORRECTION… " in our climate" written on the above posting should of course read “in your climate”

I have not seen disease on it whatsoever in my area. I used to be a wholesale inventory manager. One of our crops was Knock Out, Double Knock Out, Pink Knock Out, Double Pink Knock Out and Rainbow Knock Out. We sold at least 30K of them per year. The only one to ever show any disease was Rainbow Knock Out. It mildewed like clockwork.

For what it is worth,w e also grew the Flower Carpet series. Pink, White, Yellow, Amber and Red were less disease resistant than Pink Supreme and Scarlet by far. Scarlet has foliage like plastic that seemed to care less how tight they were packed into a row.

So, by “here”, I specifically mean the Tualatin Valley of Oregon, USA :slight_smile: In relativity, I believe Paul lives in the Willamette Valley, which is both south and east of “here”. The Tualatin Valley is slightly more wet locked between slopes, which creates a lot of dense air and constricted air flow, than the Willamette Valley.

Thans for your detailed answer, Michael. It is shocking to me to hear that ANY rose is free of disease…I have never encountered this, ever, here where I live…I think part of the reason has to be that no roses that exist in my area were actaully bred in my area.

Having said what I just said, the truth is that it still IS possible there are some selections already here that are totally clean which I simply have not seen yet…I’ll be keeping an eye out for them, to be sure! (in particular I’ll endeavour to see how Pink Supreme FC and Scarlet FC perform here…if I can actaully get them).

The provenance could play into it. If they ever were grafted, your plants could be weakened by virus. That said, we would all be better served if every assessment of any cultivar came with all the caveats as to where it does well.

(Don’t get me started again on the “All-American Rose” selection… When I live in “all America” I’ll start caring…)

I don’t tend to think of Sydney as being quite as wet and warm as the Gulf Coast of the USA, but here the only disease-free rose I have is banksia. It can mildew, however, in the NW states, and has little cold tolerance. When I have room for my R.b.Lutescens, I look forward to playing with it nonetheless

I’ve almost been driven to changing my hobby to breeding tropical hibiscus… But then we do get occasional freezes.

The main problem with All-American Rose is it is not based necessarily on the best rose but more on what they think is the best marketable rose. Plus until recently they sprayed and sprayed and sprayed. Here is an interesting thought how many pink roses would be voted as All-American Rose winners if they toke every characteristics into account as equals and truly picked the best overall rose? And heaven forbid if they strayed from exhibition type (with a few exceptions)? I think they need a new award for the best bedding plant that home gardeners can truly trust in?

lol its more useful for me to see what wins in the UK. Their roses typically shine here. A lot of German roses typically do well here, too. In contrast, French roses are often AWFUL here – with some rare exceptions (like some of the meidiland landscapers).

Flower Carpet Scarlet is a great rose here. Grows well but not 100% clean (I often think this is an unrealistic and irrelevant goal… show me ANY plant ANYWHERE that is 100% free of so form of disease)… it’s all about degree and overall effect I think. Flower Carpet Scalet is fertile and is the seed parent of my best seedling for the season which so far taps head is growing strongly and cleanly. ‘Immensee’ is growing cleanly here as is “Temple Bells”. I’ve not seen ‘Knockout’ offered for sale here. Keep an eye out for one called ‘Little Wonder’. It is fertile and healthy and a compact miniature that I think has a lot to offer and is along the lines of these wichurana-based hybrids (in a more controlled form).