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." ----------------------------------------------------------------------------- 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." ---------------------------------------------------------------- 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."

James Galway gets over 20 feet tall in late fall as 7th-year-own-root in my zone 5a. James' Blooms has amazing carnation scent when aged in the vase. It lasts 5+ days in the vase. Below bouquet was taken mid-July, showing pink Comte de Chambord, and bright-red L.D. Braithwaite at center (lasts long in the vase, but not much scent). Left yellow is Golden Celebration (form is bad in hot & dry). Dark reds are W.S. 2000, it's a continuous bloomer as 12th-year-own-root. Lavender Crush is good for the vase, it used to be deep ugly purple, I don't like the color so I dug out the top 1 foot of clay and mixed pelletized lime to soften the color, and it has been 100% healthy with zero blackspots, plus the color is lighter & prettier: Below pic. showing Lavender Crush with zero blackspots as 7th-year grafted-on-Dr.Huey. Pic. taken this August 11, 2022. It's over 5 feet tall and blooms at the top:

Good idea, Jim, that would be sturdy & easy to clean. What store did you get it from? I will have to look for that. One healthy rose worth buying: William Shakespeare 2000, I never find any Japanese Beetle on that for the past 4 years, since its petals are tightly-packed, and JB can't get inside. I have W.S. 2000 in a flooded area, with the overflow of rain barrel dumping water on that tiny rose, yet it's clean. I also put gypsum (for its zillion-petals), and cracked-corn in the planting hole (for anti-fungal agents in corn, such as zinc and copper). How one prepare the planting hole determines how disease-resistant it is. If the hole is well-drained, and has beneficial microbes, it will be healthy. When I piled up horse manure on Golden Celebration, I was surprised that the previously compacted soil underneath is made fluffy, thanks to the microbes from the well-rotted manure. The below link explains why: http://www.naturalenviro.com/Article.php?ArticleSKU=Soil-Building "The broad and diverse population of soil microorganisms will immediately begin to build an aerobic zone in the soil. The aerobic zone is the top portion of the soil that supports plant life. A healthy soil will normally have an aerobic zone 8-12 inches deep. Most soils today have an organic matter content of less than 1% and usually have very shallow aerobic zones (1-2 inches). One of the main causes of this is the lack of diverse population of beneficial soil microbes. Soils that have low organic matter and shallow aerobic zones also have a very low water holding capacity, are compacted, and have very low oxygen content. These conditions are very adverse to good root development by turf or plants and usually indicate very low microbial activity. When you apply microbes, you will see conditions in your soil begin to change quickly." An excerpt from another site on humus: http://www.naturalenviro.com/Article.php?ArticleSKU=humic-acid-role "Humic acid is also especially important because of its ability to chelate micronutrients increasing their bio-availability. Humic acid stimulates microbial activity by providing the indigenous microbes with a carbon source for food, thus encouraging their growth and activity. Soil microbes are responsible for solubilizing vital nutrients such as phosphorus that can then be absorbed by the humic acid and in turn made available to the plant. Additionally, microbes are responsible for the continued development of humus in the soil as it continues to break down not fully decomposed organic matter." William Shakespeare 2000 as own-root can take lots of rain. I look over the pictures over the last 4 years, including the 1st year when it was in a pot, with chemical fertilizer. My rating: it was really stingy in a pot, from high-nitrogen-soluble. It gave lots of bloom with sulfate of potash & gypsum, but the health can't be compared to horse manure. This year with too much rain: I used red-lava-rock & cocoa mulch, bloom-quality is good, but leaves got holes from excess water, but no black spots. Below is William Shakespeare when I used horse manure & alfalfa meal, 100% healthy, fantastic bloom-color and quality: Here's William Shakespeare 2000 bloom with horse manure: nice purple, thanks to the trace elements in horse manure. I like more than what I have now, deep crimson from red-lava-rock:

Here's the recipe from Gardenknowhow site: https://www.gardeningknowhow.com/plant-problems/pests/pesticides/epsom-salt-for-pest-control.htm "Epsom Salt Solution Insect Control – A mixture of 1 cup Epsom salt and 5 gallons of water may act as a deterrent to beetles and other garden pests. Mix the solution in a large bucket or other container, and then apply the well-dissolved mixture to foliage with a pump sprayer. Many gardeners believe that the solution not only deters pests, but may kill many on contact. Dry Epsom Salt – Sprinkling Epsom salt in a narrow band around plants may be an effective means of slug control, as the scratchy substance abrades the “skin” of the slimy pests. Once the skin is effectively roughed up, the slug dries up and dies." From Straw: The epsom-salt-solution spraying is more effective than the dry-epsom salt for MIDGE. Why? Cornell University research on midge showed that midge larvae needs a certain % of moisture to hatch. I posted that research in 2014. Midge doesn't like it too dry nor too wet. One recommendation was to flood the area. My high-magnesium clay is SOAKING WET when it rains, but BONE-DRY when it's dry, so midge larvae can't hatch. Epsom-salt (magnesium sulfate) is neutral pH, so it won't hurt plants if you flood only the top 1/2" of soil. But if too much Epsom-salt solution gets to the root-zone, it'll make soil too dense for root-growth.