Two days before there'd been no sign. My mallow, grown from a collected seed pod, was thriving, and I was looking forward to the first flowers. And then I go out to water, and what do I find - yellow, streaky wilting leaves.
What can you do about them? First of all, there are preventative measures. Simply misting the plants helps - pay particular attention to the back of the leaves, where the mites congregate. They thrive in hot, dry conditions - just what we have here on the balcony, and which are found in other enclosed spaces, like conservatories and greenhouses - so increasing the humidity helps. Before the infestations hit, I also spray with a mix of garlic, onion, cloves and cayenne pepper - but it doesn't kill off the mites if they do get a hold. Once that happens, the best thing to do is to pick off all the infected leaves, spray with water (or the mixture above) and wipe down the underside of all the remaining leaves. If you live somewhere where you can get them, there is a predatory mite - Phytoseiulus persimilis - which will clear any that you missed. If not, you may have to resort to spraying.
There are organic sprays on the market which you can use. I can't get them here so I can't comment on how effective they are, but I've spent the last month searching for Neem Oil - supposed not to harm bees and other insects - and according to this article by the RHS, even the chemical companies produce organic sprays.
If you must use a chemical spray, choose one which specifies that it kills the eggs as well as the adults or you're wasting your time. If you combine it with misting and wiping, you should also be able to keep the amount you use to a minimum.
But even chemical sprays will only work if you catch them early. If not, give up. Pull the plant up and throw it away before the rest of the balcony, conservatory or greenhouse is affected too.
I seem to have caught my mallow early enough to save it. It looks a bit straggly where I've pulled off the leaves, but what remains seems green and healthy. And the infestation doesn't seem to have spread to anything else. But I know this is only the beginning. It's going to be a long hot, summer ...
There is of course another remedy, if you're really desperate. Just take the initial s off the word spraying, and possibly you have the only thing that could really work ...