Natalie, While Japanese maples should not need spraying in-general, there are some of us that have taken to doing it, whether for good or for bad. I use Pyton 27 as a dormant spray late in the winter and again just as the buds begin to swell. It can be used on new foliage or as a soil drench during the same time frame. This can also be combined with the Bayer Disease control product that contains and antifungal and mixed in the same sprayer. For any bark or trunk related problems, I will use one or both from the above with a sulfer spray, but I do not use the sulfer spray dormant in the canopy, only for isolated spots. It must be sprayed alone and is not able to be mixed with the others. But again, in our area which is a pretty hot dry valley with only moderate moisture in the winter, there is really no need to proactively spray. Areas will differ. Michael

One advantage of using organics is it benefits earthworms and soil microbes. Chemicals, be it Bayer spray or chemical fertilizer can upset the flora of soil microbes, giving rise to pathogenic fungi. Even gypsum (23% calcium and 17% sulfur, salt index of 8) caused rust on the metal scoop. It's corrosive and killed soil bacteria, resulting in rust and black spots when I applied too much on the surface. Organic fertilizers nourish beneficial soil microbes. Here's an excerpt from the below link on organics fertilizers: "Yum Yum Mix 2-1-1 Alfalfa Meal: Nitrogen; Vitamins-A, B, E, carotene, thiamine, biotin, pantothenic acid, niacin, riboflavin, folic acid, choline; 16 amino acids, co-enzymes, sugars, starches, protein fiber Cottonseed Meal: Nitrogen, Phosphorus, Potassium Kelp Meal: Nitrogen; Potassium; Vitamins-A, B, B2 , C, calcium, pantothenate, niacin, folic acid; minerals-barium, boron, calcium, cobalt, copper, fluorine, iron, magnesium, manganese, molybdenum, nickel, sodium, strontium, sulfur, zinc; 17 amino acids Greensand: Iron, Potassium, Silicate, Phosphorus, 30 trace elements Rock Dust: Calcium, Sulfur, Magnesium, Boron, Cobalt Rock Phosphate: Phosphorus, Calcium, Trace Elements Humate: Salts of Humic Acid ��" improve soil characteristics and aids in releasing other nutrients to plants in usable forms Dry Molasses: Carbohydrates, Sugars, Trace Elements ��" feeds and attracts beneficial soil organisms." *** From Strawberryhill: When I research on endo and ecto mycorrhiza fungi that access nutrients for plants, they thrive at pH below 7. The sugar in molasses feed these fungi that help plants to utilize nutrients in soil. Here is a link that might be useful: What's hiding in your organic fertilizers?

Hi Jim: thanks for the picture of the mountains in your PA area ... that's so beautiful !! I live 1/2 hour northeast from DeKalb, IL. You are right that DeKalb is flat, mostly corn fields. I have more trees & and varied scenery here. My heavy clay is fertile too. I don't need to fertilize much, but I need to add trace elements for disease-resistance. This is my first year WITHOUT horse manure, and it's the most black spots, and disappointing year !! Horse manure NPK is low, but high in trace elements, thanks to its being a good source of bacteria. Plus zinc and copper vitamins added to the feed. Even if the soil is tested sufficient in NPK, with constant rain, and after heavy blooming .. nitrogen and potassium are leached out. Nitrogen can be re-supplied again with nitrogen-fixing bacteria, which is abundant in organic matter like composted manure. But potassium has to be supplied via fertilizer. Henry Kuska, professor of chemistry and once had a garden of over 1,000 roses, made an excellent observation that perhaps roses become depleted of potassium after a bloom cycle, esp. late fall. I agree, I gave Comte de Chambord a big-dose of potassium at the start of its 2nd flush ... it gave many petals-bloom, and the bulk of the blooms are heavier than the leaves plus the wimpy root. Now at the end of its flush, it's breaking out in B.S. To make zillion-petals bloom, a lot of potassium and calcium are needed prior to each flush. Less-petals like Knock-out are more disease-resistant, because the bulk of its roots is more than the bulk of the blooms ... the roots can easily fetch more nutrients. So for wimpy-root roses like Comte de Chambord and Jude the Obscure, immediate soluble fertilizer is needed for blooms & disease-protection. Why Mr. Lincoln is more disease-resistant for your soil than else where? Perhaps Mr. Lincoln root is most vigorous in your particular soil to fetch the nutrients needed to fight against diseases. Romanticas are clean in my alkaline soil, since their roots are very vigorous at my soil pH, with plenty of dolomitic lime for them. Your pic. shows the mountains in PA, which means less air-flow than my open Chicagoland. Plus I don't get dew, as you stated, "Here we get heavy dews outside. So around 10pm the leaves on our roses are getting wet as if it rained. They dry off early to late morning so perfect breeding grounds for BS." I find that dry & leathery leaves like Crimson Glory (prone to mildew in dry climate) tolerate wetness on its leaves. Crimson Glory is my top-clean rose, even after 1-week of constant rain. Same with shiny leaves like Pat Austin ... that one is known as a water-hog & loves the rain, but become droopy in hot & dry weather. Christopher Marlow has thick & shiny & rain-resistant leaves. It's the thin-leaves like Comte de Chambord that can't take the humidity nor wetness. I have to give that SOLUBLE calcium & potassium to make its leaves thicker. Same with Gruss an Teplitz, leaves can't take wetness, and he's the parent of Dr. Huey rootstock. Zinc and copper are the 2 strongest antifungal agents, and some soil are more deficient in those. That's why this year without horse manure, my roses are the worst ever. Calcium is a weaker antifungal agent, but it still works. That's why my Duchess de Rohan planted in my clay fixed with tons of gypsum, is 100% clean despite being a shady, perpetually wet spot where other perennials are mildewed, and other roses with BS. My clay is dolomitic lime, and I'm next to a limestone quarry, yet my soil is tested barely adequate in calcium. One hundred plus-petals bloom like Austin roses require lots of calcium and potassium, versus less-petal Knock-out. Below is a bouquet picked today, July 23, showing the many petals roses. The firm-petal one like Stephen Big Purple which lasts long in the vase, also requires an ungodly amount of calcium. It does very well next to my limestone-based patio, and doubled in growth after application of gritty lime. Pink is Sonia Rykiel, yellow is Golden Celebration, small beige Mary Magdalene, big peachy pink are Evelyn. This post was edited by Strawberryhill on Wed, Jul 23, 14 at 22:56

Nope, Diane is right -- it is the grafted variety, not the rootstock that is prone to disease, and determines resistance to disease. The exception to that is when they use an already diseased rootstock -- usually with RMV (rose mosaic virus) -- which happened in the past, but I have not seen diseased rootstock recently with any of the major growers. Other than that, the Dr. Huey roots probably lend the overall rose more, not less, vigor than the original roots (which is probably why that particular rose is sold grafted these days, when the grower can choose either one), and which would also give it more vigor to fight off, or even to grow through, fungal diseases. If you are seeing more disease on the Dr. Huey grafted plants, it might be because that variety was not only not strong enough to grow on its own roots (think Pope John Paul II), but also not a particularly strong variety on the disease front either.