Hi - I have a problem with my Salvia (nemerosa, I think ) 'May Night'. The previous owner planted it all over the place, with different exposures, likely different soils, etc. but they all look bad. The first thought that came to me is that they're chlorotic, but I would be surprised that *all* of them are, unless they're heavy feeders or something (I'm not known for my use of fertilizers). But if you're not familiar with the plant, the leaves are usually a uniform medium to dark green.
A neighbor suggested a fungus - if so, it's not living on the leaves, per ce - there's nothing to scrape off or anything.
I'd check the underside of the leaves for spider mites. It's not chlorosis (salvias don't need a lot of fertilizer anyway) and it doesn't look fungal, but it could be spider mite damage (or some other sucking insect). I've had problems with spider mites on my salvias in the past, they're one of the few pests that I've found that enjoy the taste of salvia.
If you're not familiar with SM's, they are very, very tiny, look for teensy little brownish or reddish brown dots on the underside of the leaves. If it's a bad infestation you may find some webbing on the undersides as well.
You can place a 8.5 x 11 white sheet of paper under a plant and shake it to see what falls down. SMs will appear as very tiny dots that move on the paper. In a really bad infestation, you will notice some webbing as seen in the picture link below:
Natural predators, Insecticidal soap, horticultural oil, neem oil, Bayer Tree and Shrub Insecticide can be used in a sprayer to combat this pest. For either pest, spraying the underside is critical because that is where these pests hide. I have also used systemics to control this problem in my azaleas but I apply them in March/April.
Note: if you apply insecticides/oils, re-apply again later per label directions to kill any pests that come out of eggs that hatch after your first application.
Note: if you apply insecticides, do not release lady bugs and similar predators of SMs and lacebugs because the insecticide will indiscriminately kill everything it comes in contact.
If it is spider mites, water sprays alone will control them. They don't like wet feet. Spray the water up under the leaves, several days in a row, and repeat again a few weeks later for any eggs that may have hatched afterward.
Although I prefer the systemic pesticides because they don't kill the good guys, I don't use them on flowering plants that attract butterflies. And Salvia attracts butterflies. However, according to the director of Cockrell Butterfly Center in Houston, insecticides made of imidacloprid (which is systemic) are not toxic to butterflies.
Thanks for your input, you three. It does appear to be spider mites.
Ceejaytown, that was always what I had been told, too - I'm just surprised that we have them as we've had a fairly wet summer. I was thinking about a water/soap spray for a few days, but I've really no idea if the soap will do anything in this case or not.
I've also had good luck controlling mites with the hose--usually though I get them on my container plants so it's easy to just tip the container on its side and give the undersides of the leaves a good hosing off. A little harder to do with things in the garden, but it's definitely the least toxic way to go. As far as the systemics--I have read some things suggesting that imidacloprid is toxic to bees. I have never thought about using it in my garden anyway so I never really dug in to see what the evidence was one way or another, but it's something you might want to look into if you were considering going that route.
Since it hasn't been determined (scientists are looking at a variety of factors), and even though it appears at this time that imidacloprid is not involved, it is still best to avoid the widespread use of any pesticide. I HAVE looked into it, since it has become the first recommended pesticide when applicable at Extension. I still have my concerns.