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Black spots on my rose leaves..... sunburn? :P HELP please....

Gardening Reference » Gardening in 2004
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by Diah Djoko on October 21, 2004 07:19 PM
Hi [wayey]

I'm Diah, a newbie at gardening.
Several months ago I bought a couple of roses from a nursery (it's a common type in Indonesia but I have no idea what it's latin name).
The rose crown is not dense at all and its fragrant can only be smelled when we put our nose right into it [flower]

I plant them in large stone containers, water them regularly (except when it's raining like these past few days), and fertilize them with a 20-20-20 solution every week (roughly about 250 ml per plant).
They've been doing fine and new leaves and buds are sprouting here and there.

This morning I noticed that some of the leaves have black spots with yellow hallo. [scaredy]
Can anyone please, please help me explain what those spots are and how I treat them?

Thank you..... thank you...
Diah
by papito on October 22, 2004 05:52 PM
Symptoms---Circular black spots with fringed margins appear on leaves. Leaves may turn yellow and drop prematurely.

Problem---BLACKSPOT. A fungus disease, easily spread to nearby bushes by rain or hose. Overwinters in small cane lesions or leaves left on the ground.

Solutions---Water with want or soil soaker. If you must wet foliage, do it early in the day, so the bush can dry before night. Spray regularly with Funginex or any brand of fungicide available in your area. Baking Soda can also be used to treat blackspots in roses.

From the same article:
quote:
An article in the June, 1990 issue of Greenhouse Manager magazine summarizes the results of three years of testing baking soda as a fungicide for roses. Cornell University researcher Dr. R. Kenneth Horst observed suppression of PM and blackspotóboth major problems for New York rose growers. Roses were sprayed every 3 to 4 days with a water solution of baking soda and insecticidal soap. The latter was included for its surfactant qualities. (Surfactants are chemical agents that alter the surface properties of a liquid.) The soap improved the effectiveness of the bicarbonate by making it stick to, and spread evenly over, the leaf surface. Further experimentation proved that the insecticidal soap itself was not responsible for suppressing the diseases. While no specific concentration of baking soda is indicated as being most effective in PM suppression, the article states that a 0.5% solution was most effective in preventing blackspot (3).


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