How to Treat and Care for your Roses
Commonly known simply as The Black Spot, the small circular black spots with fringed edges cause leaves to yellow, and being that they are signs of a disease. Leaving the affected leaves on the plant can allow the disease to spread, so you should remove the infected foliage and pick up any fallen leaves around the rose. Artificial sprays may be used to prevent or treat it.
If you notice that the leaves on your rose plants start to curl and turn purple, you should check the leaves and canes for a white powder, as these may be signs of a fungal infection known as powdery mildew. Spread by the wind, it may cause the canes to become stunted or malformed. Treat using Funginex or Benomyl.
Also know as rust, you may notice that the leaves on your roses may have orange-red blisters on them that turn black in the fall. It is important to remove these leaves in the fall, as the diesase can survive the winter and spread to new plants in the spring. A spray every 7-10 days with Funginex or Benomyl could help.
If you start to see yellow, red, or green spiders on the undersides of the leaves on your roses, you have spider-mites, which will suck the juices form the leaves the longer they are there. they are easily detected by spotting the leaves and flowers that are stunted or malformed. You can use Isotox or Orthene to aid you in treating this infestation.
If you notice mottled leaves, or if the leaves have small white webs under them, chances are it was caused by aphids. The brown, green, or red bugs have a soft body, and are often found clustered underneath the leaves and flower buds, and will also suck juices from tender buds. You can treat this with Malathion or Diazinon spray.
If your flowers appear deformed when they open, or if they don’t open at all, you could have Thrips at the source of the problem. The slender brown-yellow bugs with fringed wings can also be found sucking away at the juices of the leaves. Use Malathion and Orthene to treat.