I would really appreciate advice on how to treat my poor diseased bromeliads. At the end of the summer I began to notice spots on some of my bromeliads. The spots are pale and some have a black dot in the center. The spots look much the same on the underside of the leaves. The bromeliads pictured are billbergia pyramidalis and they seem to be the ones mostly effected. I am not sure what the cause is, but I sprayed them with Daconil (chlorothalonil) mixed at a rate of one tablespoon per gallon. Their appearance has not changed much since then. These are growing outside in my central Florida garden.
Help for diseased bromeliads
I suppose it could be scale. If I scrape the dots with my fingernail they will come off. They are tiny and not very raised on the top and underside of the leaves. If it is scale, how do I treat it? Thanks for your help!
I have some spots like that on some of my broms, too. I'm not treating them with anything, since the plants seem healthy otherwise. They're blooming, making pups and generally healthy. Yours look healthy with nice shine to the leaves, to me, too. I think it's just cosmetic. The older leaf rosettes do get looking ratty eventually, after they've made several new pups. Do the newer leaves on the pups have the same spots? If not, you can just separate the old rosettes and remove them. Once they've bloomed and made a few pups they're pretty much done anyway.
You're more likely to harm the plants (not to mention yourself, your pets, and every living organism in range) spraying them with chemicals, in my opinion. Always start with an informed decision, then the most benign treatment you can, and work up to chemical warfare materials like Daconil as a last resort. You can take a leaf in to your local County Extension and get somebody to look at the spots under a microscope. It's not a good idea to "treat" a plant for something if you're not sure what the affliction is.
I think it's more likely fungal than scale. Try spraying the leaves of unaffected plants with a solution of baking soda and water, 1/2tsp. of soda to a quart of water. It won't take away spots that are already there but it will prevent the spread to clean plants. This is a soluble spray, so you'll need to re-spray at least every week or after it rains.
All the older mother plants in this picture have a few of those spots. The new ones are clean. I'm just going to remove the mama plants next week to give the babies room to grow and bloom.
Looks like scale to me. While I try not to rely on chemicals either, it it spreads you may have no choice.
First, I'd isolate this plant so that if it is scale it won't spread.
Get a jewelers loup (maginifier) and have a close look at those areas. They look like the crawler stage after the eggs hatch. The "crawlers" do just that, than stop and start morphing (terminology?) into adults. They are easily killed by hand and a good water spray but it's difficult to get all of them. They often hide in small folds of the leaf and in the leaf axils. More often than not they are on the undersides of the leaves but once they get going they will be all over.
I'd try physical squishing (doesn't take much force ) followed by a good hosing water stream onto the grass to flush off any remaining eggs.