Question
QUESTION: I have a climbing rose that was plagued with aphids and worms.  Bayer Rosecare cleared that and it finally grew tremendously and even flowered. It gets morning sun 'til afternoon.  It's hot now.  I water 1-2 times a week
Lately, leaves are turning yellow, even some growing in yellow.   On some leaves, there a powdery film underneath with black specks, like soot.  After removing some of the leaves (damaged stems just break off) my fingers feel dirty, like dusty.
It doesn't look like mosaic.  I don't think it's over watering, especially since it's been very sunny, though living in Santa Monica, we had a foggy July, and sometimes morning overcast.
I had some mildew on a neighboring plant, and was guided to spray with water mixed with soap and oregano oil.  Could these symptoms be a reaction?  (The mildewed leaves on the other roses turned dark brown)
Thank you.


ANSWER: Aphids suck the juices out of the new growth  and when they do they exude a sticky substance with black specks in it. This sticky substance can also attract fungal diseases. Because the rose has been under attack from insects and worms, plus the high heat, the roots have gone under stress. This is normal and will show up by dropping the leaves which have turned yellow and died. Many gardeners are having the same problem with their roses because they are experiencing a wave of hot weather. Using soap or oil on rose leaves is not a wisdom as the soap can burn the leaves and the oil will stop the ability of the leaves to breathe. In your area mildew can be a big problem and if you first see it, try using a simple spray to get rid of it. Once it has taken hold it will kill the leaves and finally when the  rose is covered with a white mould, the rose will suffer and die. 1 tablespoon of baking soda to 2 quarts of water sprayed daily should stop it when it first starts. When the mildew has really taken over, you will need to use a fungicide for roses. The fact that the bayer spray got rid of the problems and the rose did well, tells me the rose is just re-acting to the blast of heat. I know the rose books tell you not to  wash a rose bush down with water  because it cause black spot, but that myth has been put to rest. When roots go under stress, they are unable to do their job of transporting water and nutrients to the plant. However leaves can take up water plus fertilizers so washing the bush down when it is hot is a good idea. Don't give your rose any fertilizer when the weather is hot as they could burn the roots and damage the rose bush. Wait until the weather has cooled off. Actually in your area roses really don't need any more food now until the spring.

---------- FOLLOW-UP ----------

QUESTION: After I wrote I looked again at a second bush and think it may have mosaic virus on lower leaves.  It is splotchy yellow  with a freckled green look - different than the all-over yellow on the first plant.  This plant is healthier overall.  Is there a natural way to treat mosaic?  Thank you very much for your replies.

Answer
When roses are under stress, they will get rid of the lower leaves. Before they drop them the leaves turn a yellow with speckles and a pattern that looks like mosaic virus but isn't. This virus usually turns up on the upper leaves as well as the lower leaves so I am sure the rose is okay. Thank goodness you don't have mosaic as there is no cure for it.