The idea here is to change the P.H. level on the leaves so to create an environment inhabitable to the fungus that creates black spot.
This particular recipe calls for 1 tsp of baking soda per liter of water with 1 tsp of (non bleaching) dish soap.
Combine & agitate. Spray on both sides of leaves.
Avoid spraying while in direct sun. Arrange to spray at least an hour or two before the sunlight comes around if possible.
Repeat weekly and after rain.
Additional tips to keep the susceptibility to fungus down is to assure dropped debris are cleared from beneath, on and around the plant(s) before spraying. Burn this debris rather than composting.
Just before Spring rolls into high gear is a good time to conclude this type of clean up, that may have been started in the fall.
After the last frost is the best time to fertilize with a healthy application of amended top dressing before mulching. Bark is my preferred mulch for all rose plantings.
When watering, avoid water pressure hitting the ground forcing water up from the soil onto the plant. Drip is the best way to water these susceptible crops.
It would be interesting to hear from reader’s who go ahead and try the above recipe.
What natural organic pest control resources have worked for you to control black spot in your gardening regime? What hasn’t worked?
Please feel free to comment.