TREE AND SHRUBSLeaf it to me

My Roses Have Terrible Black Spot; Help?

This is a question for all you experienced rose-handlers, out there.

Black spot is caused by the fungus Diplocarpon rosae. The black spot fungus over winters in fallen leaves and in lesions on infected canes. So the treatment for the disease must include the canes or they will serve to reinfect the rose later.
Your mulch under the rose will help but is only part of the job. Dust the ground around roses with cornmeal, and water in. This helps to eliminate black spot spores that attack roses, and also helps to eliminate the spores in the soil around roses. Work in corn meal at 2 pounds of cornmeal for every 100 square feet. Water well to activate the fungus killing properties. There is a cheap, nonfood grade available at some garden centers.

Immunox uses an acropetal/basipetal bidirectional movement so is locally systemic in its effect.
I would add another to be sure not to breed resistant fungi.
Fosetyl aluminum; Aliette is the only truly systemic fungicide, moving to root and crown, so is the really bid gun in treating BS. Note that it is carcinogenic so use full precautions in spraying this.
Another group to consider is Thiophanate-methyl found in Cleary’s 3336, Domain, Halts Systemic, Greenlight Systemic, Topsin M. Class IV toxicity so much safer to humans and other mammals.
One from those two groups in addition to Immunox then you need a contact fungicide to maintain prevention once you have this infection under control.
Contact fungicides remain on the leaf surface, acting as an exterior shield. They provide a barrier to protect against infection by fungal spores so they must be applied before infection and very completely. Baking soda/horticultural oil — Tests performed by Cornell and Auburn universities in the U.S. confirm this as a good powdery mildew control. Mixed at a rate of 4 tsp baking soda (sodium bicarbonate) and 1 tablespoon horticultural oil per gallon of water, this material is sprayed on foliage and stems weekly before the disease first appears. Use caution to keep the spray confined to the plant foliage and canes, thus reducing the potential for sodium bicarbonate buildup in the soil.
Neem oil works well & is a miticide.
Sulfur and sulfur compounds — Both wettable powders and premixed solutions are currently available. But must not be used within two weeks of horticultural oil.
Come winter a dormant oil should be used in Feb & Mar or until the first leaves appear. Then the contact sprays will be sufficient and less harmful.
Vinegar Fungicide
Mix 3 tablespoons of natural apple cider vinegar in one gallon of water. Spray during the cool part of the day for black spot on roses and other fungal diseases. Adding molasses at 1 tablespoon per gallon will again help.
. Garlic naturally contains high levels of sulfur and a few cloves crushed in water can be used to make a homemade spray.
To make garlic tea, liquefy 3-4 bulbs of garlic in a blender 1/2 to 2/3 full of water. Strain the solids and add enough water to the garlic juice to make 1 gallon of concentrate. Use 1/4 cup of concentrate per gallon of spray. Add 2 T of blackstrap molasses as a sticker.

Another really good method is milk spray …… In 1999, a Brazilian scientist found that milk helped control powdery mildew on cucumbers just as effectively as a synthetic fungicide. So far, there has been success reported on the use of milk to control powdery mildew and black spot on roses.
Any type of milk can be used from full milk to skim to powder. However, the low fat milks produce less odour. The recipe calls for milk to be mixed with water at a ratio of 1 part milk to 7 parts water and applied every 5-7 days for 3 applications.

Every leaf infected will stay that way, the black spots will not heal. You have to be patient for the rose to regrow new foliage. Spraying the rose with kelp & fish emulsion will help give it a boost towards recovering.

ZeroTol Ready to Spray Fungicide/Bactericide

Ortho 0295160 Rose Pride Rose & Shrub Disease Control – Pint $13.27 Funginex Rose Pride Disease Control Shrub & Rose Disease Control Controls black spot, rust, and powdery mildew on roses, flowers, shrubs and shade trees. One pint makes up to 32 gallons of spray. Endorsed by the American Rose Society. Black Spot is one of the most common fungal rose diseases. It is characterized by rough, round spots appearing on the leaves. Infected leaves will turn yellow, and f…

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Bayer Disease Control for Roses & Flowers – 32 oz. 701250B $19.99 BAYER DISEASE CONTROL 32 OZ.Cures and prevents diseases that harm roses, flowers, trees, shrubs, and house plants. Controls all major fungal diseases including black spot, rusts, powdery mildew and more. Systemic protection lasts up to 2 weeks. Exceptional value – 1 quart makes up t…

The Scotts Co. 0347060 RosePride Rose and Shrub Disease Control $12.43 Controls and protects against all major rose diseases. Endorsed by the American Rose Society. Controls black spots, rust, and powdery mildew on roses and other ornamentals. Leaves no unsightly residue on foliage or blossoms. Can be combined with Isotox insect spray for use in sprayette. 1 pint makes 32 gallon of diluted spray. Contains: 6.5% Triforine. Pint bottle….

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