After using the Cornell spray for several years, mine have required no spraying now for the past three years. But that also means I haven't brought any new roses in within that period.

That's great news Field! I was hoping to hear that roses somehow learn to fend for themselves after a few years. Your experience seems to confirm that.
Thank you for your input,
Angie

The rose has no physiological "memory" of being sprayed in the past months or years with fungicides. They are not "addicted" to past use. They do not "adapt", they cannot "learn". New leaf tissue is new leaf tissue.

If you get the soil improved so that the roses can grow happy and healthy they can adapt to a "no spray" life.

Until the black spot mutates, which it will. YOu can slow things down by not introducing new strains into the garden, like Field above. BUt, for most people, it isn't practical to never buy new roses. You can quarrantine new garden entries, but if they're bands or other small ownroot babies, I wouldn't recommend defoliating them as it may set them back too much. So, you're left with a quarrantine area to grow roses in for at least a year and then to overwinter them somewhere they won't freeze until you are able to get in a couple of dormant sprays with lime sulpher. For larger grafted roses, you can defoliate them with a lime sulpher spray and go ahead and plant. But, they'll be set back from losing their foliage too.

Title: Aspects of plant intelligence.

Author: Trewavas, Anthony

Author affiliation: Institute of Cell and Molecular Biology, University of Edinburgh, Edinburgh, EH9 3JH, UK.

Published in: Annals of Botany (London), volumn 92, pages 1-20, (July 2003).

Abstract: "Intelligence is not a term commonly used when plants are discussed. However, I believe that this is an omission based not on a true assessment of the ability of plants to compute complex aspects of their environment, but solely a reflection of a sessile lifestyle. This article, which is admittedly controversial, attempts to raise many issues that surround this area. To commence use of the term intelligence with regard to plant behaviour will lead to a better understanding of the complexity of plant signal transduction and the discrimination and sensitivity with which plants construct images of their environment, and raises critical questions concerning how plants compute responses at the whole-plant level. Approaches to investigating learning and memory in plants will also be considered."

Title: DYNAMIC ASPECTS OF THE CHEMICAL RELATION BETWEEN THE ROSE APHID MACROSIPHUM-ROSAE AND ROSE BUDS

Author: MILES P W

Author affiliation: WAITE AGRIC. RES. INST., UNIV. ADELAIDE, ADELAIDE, S. AUST.

Published in: Entomologia Experimentalis et Applicata, volumn 37, pages 129-136, (1985).

Abstract: "Dynamic aspects of the chemical relation between the rose aphid [Macrosiphum rosae] and rose buds.In warm weather, M. rosae (L.) walks off buds of hybrid tea roses during a critical period coinciding with the opening of the sepals. This behavior could not be related to histologically detectable barriers to feeding, nor to changes in the water content of the tissues or in their composition with respect to total soluble carbohydrate, amino nitrogen or phenolic compounds; major changes in tissue chemistry, effected by spraying the bushes with urea, did not affect the time at which the aphids left the buds. Tissue sap expressed from stems and sepals showed a significant increase in catechin content after, rather than during, the critical period. Once expressed, however, sap from buds at the critical stage showed a sharp in vitro rise in catechin content over a few hours, up to levels approximating those against which the insects discriminated in choice tests. The insects could well be sensitive to a developing capacity of tissue to accumulated catechin, possibly in response to their feeding activity."

If you are interested in reading further about whether plants are intelligent, here are 2 very recent articles:

Http://aob.oupjournals.org/cgi/content/abstract/93/4/345

http://aob.oupjournals.org/cgi/content/abstract/93/4/353

Roses will kick the chemical habit in a season or less. They will need to put down strong roots, so that depends on a variety of factors, feeding, watering, location, and so on.

HollySprings, I've never heard of mutant blackspot. Could you explain?

Thanks for all of the abstracts and links Henry. Do you have access to the full text of any of them? All look like great reading.

I have the volumn 92 pages 1-20 article.

I do not know how long blackspot takes to mutate. I am more familar with people getting a new race (variant, pathotype) of blackspot when they purchase an already diseased rose with a different race (varient, pathotype) of blackspot.

Title: Identification of five physiological races of blackspot, Diplocarpon rosas, Wolf on roses

Authors: Debener, T.; Drewes-Alvarez, R.; Rockstroh, K.

Authors affiliation: Inst. Zierpflanzenzuechtung, Bundesanstalt Zuechtungsforschung, Kulturpflanze, Bornkampsweg 31, D-22926 Ahrensburg, Germany.

Published in: Plant Breeding, volumn 117, pages 267-270, (1998).

Abstract: "Differentiation into physiological races of Diplocarpon rosae, which causes blackspot on wild and cultivated roses, was investigated with single conidial isolates of the pathogen. Infection experiments with a simple excised leaf assay demonstrated differential interactions between single isolates and a set of 10 test rose genotypes. Differential reactions could be observed among rose varieties as well as between and within a wild rose species. Accordingly, five different physiological races can be identified among the 15 isolates tested. A breeding line and one genotype of the wild species Rosa wichuraiana were found to be resistant against all isolates tested. These data will be employed in further investigations on the genetics of blackspot resistance in roses and for resistance breeding programmes."
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Title: Response of selected old garden roses to seven isolates of Marssonina rosae in Mississippi

Authors: Spencer, James A.; Wood, Opal W.
Authors affiliation: Dep. Plant Pathol. Weed Sci., Miss. State Univ., Mississippi State, MS 39762, USA.

Published in: Journal of Environmental Horticulture, volumn 10, pages 221-223, (1992).

Abstract: "Seven isolates of Marssonina rosae (imperfect stage of Diplocarpon rosae) elicited different blackspot disease expression among 39 Old Garden Roses in laboratory tests. 'Felicite Parmentier' (Alba), 'Mme. Hardy' (Damask), 'The Bishop' (Centifolia) and 'Rosa Mundi' (Gallica) showed no symptoms. 'Cardinal de Richelieu' (Gallica), 'Hermosa' (China) and 'Leda' (Damask) were the most susceptible showing a cultivar ratings mean of 2.86 or more. The Wayne variant was the least virulent, causing susceptible reactions on only 46.1% of the roses. The Hinds variant was the most virulent and caused symptoms of 89.7% of the rose plants tested. The remaining five variants caused disease on 69.1% to 79.5% of the plants."
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Title: Occurrence of pathotypes of Diplocarpon rosae on roses in Belgium.

Authors: Leus, L.; Kegelaers, G.; Van Bockstaele, E.; Hoefte, M.

Authors affiliation: Department of Plant Genetics and Breeding, CLO, 9090, Melle, Belgium.

Published in: Plant Protection Science, volumn 38(Special Issue 2), pages 536-538, (2002).

Abstract: "Monospore cultures of black spot (Diplocarpon rosae Wolf) were established from isolates collected on outdoor grown roses at different locations in Belgium. These monospore cultures were tested on rose cultivars and species with different levels of natural resistance to examine the possible existence of different pathotypes. For this purpose a screening protocol including scoring after artificial infection was developed on in vitro plantlets. Differences between the examined isolates proved that there exist different pathotypes of Diplocarpon rosae in Belgium."

That's interesting about rosebuds repelling aphids shortly before the sepals drop, thus protecting the petals. I've rarely seen more than an aphid or two on an opening flower. I was puzzled that some growers in the middle South this year said the aphids were so bad they were preventing buds from opening. One of these growers had never used insecticide, so it's not that the roses were "addicted."

On the original question, there is some kind of active principle in plants' resistance to disease, it isn't only such things as the texture of the leaf cuticle. The Fairy is highly resistant to black spot, but some of the earliest leaves of the season may show a little of it, especially those on weaker shoots, as though the plant didn't have its defenses fully up or didn't care about these particular leaves.

Whether use of fungicides reduces the plant's defenses is, I think, an open question at this point. I have noticed young own-root plants being somewhat susceptible to blackspot at first and later being more resistant. However, this might be because greenhouse conditions produce larger and softer leaves than outside conditions. The difference in foliage is quite obvious if you set a new ownroot next to an established plant of the same variety.

http://www.cpa.ed.ac.uk/edit/3.01/018.html

Here is a link that might be useful: Summary of Professor Trewavas' theory

Oh wow, looks like I have some reading to do! And I'd like to read all of this in detail before responding.

Angie

Thanks for the additional info Henry. I think Prof. Trewavas draws arbitrary distinctions such as his belief that a plant in a lab isn't intelligent compared to its kin in the wild. You could say a houseplant is much smarter because it enjoys a relatively stress free life on a windowsill with all of it's needs provided for.

Althea said: "I think Prof. Trewavas draws arbitrary distinctions such as his belief that a plant in a lab isn't intelligent compared to its kin in the wild."

My reply, he did not state that. That was a statement of the writer who interviewed him. Prof. Trewavas gave the following definition of plant intelligence on page 1 of the manuscript:

"Thus, a simple definition of plant intelligence can be coined as adaptively variable growth and development during the lifetime of the individual".

On page 3 of the manuscript he states: " Just as obvious intelligent behaviour is not so easy to detect in caged animals in zoos, it will not be readily observed in laboratory grown plants; in part, because the necessary competitive and variable circumstances to elicit intelligent responses are not present. Intelligence requires both the organism able to compute and the right environmental circumstances to elicit that computation."

Thanks for the clarification Henry. I was basing my response on the following quoted from the article.

"But, he says, you won't find plants exhibiting any kind of IQ under glass. "There's no point in looking for intelligence in house plants or in the laboratory. You've got to go out and look at wild plants or try to set up conditions like in the wild.""

He says there is no point in looking. I'm not convinced that competativeness is or should be the only factor determining intelligence.

""Intelligence requires both the organism able to compute and the right environmental circumstances to elicit that computation."" Does he mean a plant when he is referring to an organism able to compute? If so, he left out an important factor -- the observer.

I hope no one thinks I said that my roses have "learned" how to get along without spraying. I simply meant that I have pretty much cleaned all the black spot spores out of my yard -- otr at least got them down to a level where they are no longer a problem. That, coupled with increased plant health, has resulted in no need to spray.

Also, I just haven't bought any new roses and transported more black spot spores into my garden. It matters not whether that black spot would be of the same strain or not. My roses don't have any memory or any immunity, beyond that estalished by good health.

Andrea, I guess most black spot strains can be considered as mutants in some way, since over 50 different strains of the black spot fungus have been identified.

It sounds like this is a new field that needs much additional study. See:

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7CT0-4B2CDV5-1V&_user=10&_handle=B-WA-A-A-AW-MsSAYVA-UUW-AUEUEBCWVA-AUYYCAZUVA-VEUACCZUZ-AW-U&_fmt=summary&_coverDate=12%2F31%2F2002&_rdoc=6&_orig=browse&_srch=%23toc%2318036%232002%23999619999%23471365!&_cdi=18036&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=718a813e7f4d1a88ba10f8588bb806b7

Here is a link that might be useful: age related resistance