What are those white spots on all my balcony plants?

[xbr]

Hello! I'm wondering why all the plants in my balcony flowerbed look like they do on the photos I'm attaching... They all have those tiny white spots all over. I'm sure it's some sort of disease or fungus because it's happening on all 3 kinds of plants I have there. And I guess one of them passed it on to the others, because there are no other plants near them (not mine or my neighbours'). But sure enough, now all of them look the same. First it was one, the Dear William pictured, then the rosemary, and so on. They seem healthy enough (or healthy-ish) aside from the spots, but obviously this isn't normal. I'm afraid whatever it is might keep on getting worse and end up killing them and even spreading to other plants I have inside my apartment (that are completely fine up to now).

I'm currently living in Spain and it's the driest place I've ever been in. So any smattering of rain or sprinkle of water on the leaves dries completely in a matter of minutes. So can it really be fungus if it doesn't stay humid? On the other hand, maybe it has something to do with the heat? My balcony faces NNW, so they do get a bit of sun around the evenings. I never water when the sun is on them or it's too hot outside. They've been getting regular water this month that it's been REALLY hot. But now I'm laying off a bit.

Thanks in advance for any input!

 

[Marck]

Hello, and welcome to the Forum.

This type of stippling damage is usually caused by either spider mites or thrips. Look closely with a hand lens to determine precisely. If possible do post a macro lens photograph if possible. However oils and soaps can be effective with both pests.

These pests often thrive in conditions of low humidity. They also frequently infest plants that are stressed by being grown in too little light. How many hours of direct sunlight do these plants receive each day?

I would recommend treating these plants with an oil or soap. Neem oil is often a popular choice in such a situation.
However, if there are any persistent cultural problems that are not corrected, then use of pesticides can be both relentless and futile.

 

[xbr]

Hi, Marck! Thanks for your response. Well, I have been seeing small spider webs, but I imagined they were spiders. And Yesterday, upon a very close inspection, I did see these little white spiders on the webs... too small to be adult spiders, in my opinion, so I wondered: are these guys responsible for this? But then I thought: if they have webs and 8 feet, they're spiders, and to my knowledge spiders aren't pests and they don't bother plants! Bud spider MITES... might! XD They don't seem to be out right now, so I can't photograph them. But if both the possibilities you mention can be treated with oil or sopa, I might as well go ahead and try that.

Would normal hand soap or dishwashing soap diluted in water and then sprayed over them do the job?

As for the light, I shouldn't think this would be the issue, as they do get quite a lot of it. They get light bounced off the front building all morning, then indirect light after midday, and from around 4 or 5 to 8pm (if it's not cloudy) they get plenty of direct light.

 

[Marck]

Sounds good, another preventative you can try is to water the plants overhead, at least occasionally, to remove dust and the like. Always, allow them foliage to dry between waterings.

In general, many plants do benefit from overhead watering, though of course, there are also times to avoid it. When it can be decided, the decision depends on the plant, season, environment, and most likely disease or pest problem.

 

[Marck]

Sorry, I didn't answer you question about using hand or dish-washing soap earlier.
It is usually fine to use such soap, but there are many soap formulations out there so it is best to test any new usage, especially off-label usage, on a small area first. The usual concentration is about 15 mL of soap per Liter of water, though some people prefer it stronger or weaker.

 

[xbr]

*Help!*
So I tried the homemade remedy of adding some drops of diswashing-liquid to some water, as well as some drops of olive oil, which I read elsewhere can also help with these kinds of pests, and then sprayed mi plants twice during the next 2 weeks... but it seems my plants haven't liked that at all! (Or perhaps it's just been a case of terrible coincidence!) As you can see from my current photos, now they look even worse than before... and they even look pissed off, hahaha. The smaller plants that were just growing in clearly hated the dishwashing-liquid-and-olive-oil concoction. What can I do now? Is this still the mites or is it the kind of dishwashing liquid I used? Or is it something else?
P.S. If you notice in the last photo at least you can see that the rosemary now has black spots. The other plants don't have them.

 

[Marck]

I might suggest trying a horticultural oil developed for this purpose, but this is a bad infestation... Also on an isolated balcony there may not be the resources to maintain a population fo micro-predators that could keep spider mites in check. Some would suggest a petro-chemical pesticide at this point, but I'm not going to adovate a toxic 'solution' that might not be effective either.

They get light bounced off the front building all morning, then indirect light after midday, and from around 4 or 5 to 8pm (if it's not cloudy) they get plenty of direct light.

I do not think the plants are getting enough light. This does look and sound like a mostly shade location. Some plants decline and become pest-susceptible without enough direct sunlight. That would certainly be the case with Rosemary (Salvia rosmarinus, formerly Rosmarinus officinalis). If the plants aren't growing vigorously, pest control will always be an uphill battle.

I would consider replanting your containers with plants that can take shade and part sun conditions. If you want to be extra-cautious you might also replace the potting soil, though that isn't always necessary. Donate the whole pile to a local composter or green-waste facility. Keep the pots, of course. Just give them a scrubbing before replanting. There are manylovely plants that can take part sun bright shade conditions, from colorful flowers such as Impatiens or Fuchsia, to dramatic foliage plants such as Aspidistra or ferns.