|Some of the leaves on my rose bushes are curles up with webs in them. I have noticed for some time that some of the leaves have turned yellow with black spots. Also, they used to have huge, fragrant roses on them and now they're very small, not fragrant and some deformed. I don't know what's wrong. I've sprayed with an antifungal and water in the morning if it hasn't rained. I'll let them go without additional for a day or so when it's not too hot. They receive direct sun.
The webbing is probably from caterpillars. This is usually not enough of a problem on roses to worry about but if you wish to treat use a product containing Bacillus thuringiensis or B.t. once a week for about 3 applications.
The black spots and yellow leaves are a fungal problem that needs to be sprayed. Black spot fungus of rose is everywhere. If you have roses, you will have some black spot. There are varieties that are resistant and seldom get black spot. When they do it is usually not a significant problem and seldom if ever requires a spray. Cultural conditions can make black spot a rampant problem or a minor nuisance. Overcrowding, poor air circulation, and frequent wetting of the foliage all predispose plants to black spot infection.
Most varieties however, must be sprayed on a regular basis to prevent black spot infections from becoming severe. In severe cases it can even cause defoliation of the plant. There are many fungicide products labeled for black spot on roses. Your local Home Depot staff can show you a labeled product.
Other than this I suggest you work to maintain good soil moisture but not soggy soil. Try to avoid wetting the foliage when you water. Feed the roses either weekly with a Miracle Gro type soluble liquid product or monthly with dry fertilizer product applying 2 tablespoons per plant and watering it in well.
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