My Midnight Candle Salvia has curling leaves
I have two Midnight Candle salvia plants, which are annuals. One is experiencing curling leaves...curling down and inward on itself. The other plant looks quite healthy. Both are in same soil and have same sunlight and moisture. I assumed it could be aphids but could not see anything visible. I went ahead and sprayed it down with a homemade soap water spray which I use on the neighboring rose bushes. I've attached photos. One is quite healthy the other looks sad. What might be the problem?
Thank you for your question, Mary. Some leaf curls are reactions to herbicide drift, although the curling is typically toward the leaf side of the herbicide. There are a variety of problems that beset salvia, as listed here: "Salvias are relatively problem-free. They can be subject to damping-off of seedlings, stem and root rots, powdery mildew, Botrytis blight, aphids, spider mites and whiteflies. Diseases are most common either in greenhouses or under conditions that salvia dislike such as cool, wet weather. Insects are mainly problems in greenhouses."
Some sources also indicate downy mildew (on the underside of the leaf) is common in some regions. You could not find that without close examination. Extension services do not recommend soap water sprays, although some soaps sold as insecticidal may help the soft insects. But, if the problem is a mildew, soap is ineffective, certainly as compared to oils. Neem oil is a fungicide, insecticide and miticide, but application is a waste until the problem is identified.
Perhaps if you could take your photos, and some leaf samples, in to your county Extension office, they could find the cause, if it is something other than a root disease. Since you did not indicate your county, I can't direct you there, but this webpage has each county's address: http://cce.cornell.edu/localoffices