Diseased leaves?

[roadrunner]

Is this from spider mites or some other cause?  One of several plants with this and they are on Kontos.

[Charlie]

Dave, that doesn't look like spider mite damage. It's a type of chlorosis that I see occasionally but usually it is just on one or a few leaves and doesn't last long. I pull those leaves off so healthier leaves can grow back in. You could try adding more iron chelate and/or epson salts.

This leaf symptom could indicate a problem with root absorption that involves only part of the root system. That could be due to microorganism involvement or physical damage or there could be pH or alkalinity issues. It's very hard to diagnose this type of symptom, sorry to say.

Charlie

[roadrunner]

Charlie this really strange.  On some plants the new leaves have it as they emerge. On others like Tamibon the whole plant's leaves developed it over a period of a few days.  I've already tried giving extra iron chelate and fulmag of magnesium as well as spraying with insecticidal soap and a copper based fungicide.  Nothing has helped so far and several plants have it.  It also has those weird raised little brown patches on the leaves undersides.  The new growth is also stunted.  It's making this hobby increasingly frustrating.

dave

[Charlie]

These are unusual symptoms. Can you think of anything different this year compared to past years in your growing situation? Kontos may be a factor. How much are you using and how often?

Charlie

[roadrunner]

I havent changed anything.  Several plants have developed this long after I stopped using Kontos when I ran out in January.  The first time I saw this was on Ice Fairy in winter of 2010.  I didn't start using Kontos til I think August of last year.  I was using it at about 1/4 tsp per gal.  I started treating about every 30 days and increased it to every 10 to 14 days.  I ran out of Kontos in January so no plants have been treated since.  I didn't start seeing spider mites again til about 2 weeks ago.  The plants that overwintered inside the house were on Houseplant Formula all winter at the recommended dose.

Ice Fairy has never recovered and continues to have the weird chlorotic leaves.  Raging Bull is another that's had it for over a year and just doesn't recover.  I emailed Cindy several pics  that I think included the Ice Fairy plant.  I believe Cindy thinks it may be some type of virus.  If so I have 15 to 20 plants that maybe I should destroy.  Some are cultivars that only show up in the store rarely.  And of course I also have those weird shiny black spots on leaves that Bart was having so much trouble with.


dave

[Charlie]

Since we have no other good ideas, one thing you could try once summer is here is taking all plants outside and flushing the soil by slowly overwatering each pot so there is ample runoff to leach out any build up of salts from water and fertilizer. Since you keep them indoors for a long period I assume that you use saucers under them so that no leaching occurs during the time they are indoors. You can accomplish the same thing by overwatering and collecting the extra water in the saucer and then dumping this water so that it is not re-absorbed into the pots.

I suppose a virus is possible but the ones I am familiar with show as rings around a central spot on a leaf or as yellow variegation on the leaves (quite different in appearance than chlorosis) or mottling with leaf distortion. Viruses are spread primarily by insects and cutting tools that penetrate plant leaves and stems so obviously controlling insects and disinfecting cutting tools are important to prevent viruses. It's been reported that hibiscus that test positive for some viruses continue to grow and bloom normally. Unfortunately, there's not a whole lot known about viruses and hibiscus specifically.

Charlie

[roadrunner]

Several of the plants that spent the winter in the house were taken outside and rinsed off when they started getting dusty.  I would also water them several times while they were outside to do as you suggest to flush the salts out.  Unfortunately with the size of the collection getting out of hand I didn't get around to all of them and have no idea which ones I did.  The larger plants in 10" pots that spent the winter in the greenhouse/laundry room shuffle also are summered at various spots in the landscape and those received several rains which were heavy enough to flush out the salts I'm guessing.  Only one of these is showing problems currently so the rain must have helped.  Anyway will keep you posted.

Thanks,
dave

[davidwood]

Dave you sound really fed up, but for sure don't destroy 15 to 20 plants, I think you are a while from that yet. In fact if it comes to a stage where you think you have no other choise I would if I where you prune them, and not just a normal prune, really heavily prune, I have done that myself a few times [all be it for different reasons] and I have without fail always been very pleased with the results.

[Charlie]

David, that's a good point. Viruses can spread throughout the entire plant but they can also be limited to a few leaves. If the latter is the case a hard prune would do the job.

Charlie

[roadrunner]

I'm not to the point of destroying any plants yet, but am definitely getting frustrated.  I actually have done severe prunnings on about 8 plants so far.  It makes it easier to spray for spider mites and fungus.  I've done that a few times and now am spraying them with something Cindy suggested, a mix of SuperNova and Wakeup Spray.  I can't remember the ratio off hand.  Time will tell.  Also plants in the greenhouse are back on Kontos for the summer at least, gave first treatment the last couple of days.

dave

[Paul]

Hello Dave and Charles. I was wondering if either of you have ever figured out
what was going on with the hibiscus affliction mentioned above. I believe one of
my hibiscus is suffering from the same thing after reading Dave's description. I
noticed that many of the leaves started turning yellow, so my first thought was
the dreaded spider mite. When I turned the leaves over for inspection, Instead
of finding evidence of spider mites I found the same raised brown/black bumps on
the undersides of the yellowing leaves. I have treated for iron and magnesium deficiency hoping this was just some weird symptom of chlorosis, but that doesn't seem to be helping. Luckily this is only happening to one of my hibiscus (not an HVH hibiscus, thank God.). I have moved this hibiscus far away from the others, just in case. Just wondering if you have come up with any new info since these posts from May.

Thanks!!
Paul

[Charlie]

Hi Paul,

That does look like spider mite damage. If you have a strong magnifier you should be able to spot spider mites on the underside of the leaves. They look like small crabs under magnification. The best easily available mite killer is horticultural oil but it should be sprayed only very late in the day, just before sundown. To be effective every speck of leaf surface and stem needs to be covered with the spray. Clean out all old fallen leaves that may still be in the pot so that no eggs or stray mites remain to repopulate the hibiscus. It may take 3 treatments over 2 weeks to fully control the mites, assuming that this is a mite problem.

Similar appearing damage to leaves can also be caused by too dry conditions of the soil during a hot spell, or by spraying something like soap on the leaves. Spraying soap can strip the protective wax off the leaves and cause them to dry out too much. We stopped using soap products to spray hibiscus several years ago when we noticed this problem.

Last I heard, Dave was going to try giving a warm bath to a few of his plants to see if that could cure the problem. Soaking plants in 90-100F water for half an hour is a standard treatment used by farmers to eliminate microscopic mites like broad and cyclamen mites from some crops like strawberries before planting. Your affected hibiscus looks pretty big but if you have a large enough tub or barrel to give it a full immersion soak for half an hour it might do the trick.

Very smart to move the affected hibiscus away from the others until you get it figured out.

Charlie

[davidwood]

The  opening line to both paragraphs by Charlie cause me a lot of frustration, knowing which is right, is it Mites or too dry a soil, Paul I have your leaves all the time and I wish I knew the answer, I actually think it may be a mixture of both but I would give a weeks pay to know.
If I was forced to say I would go for the too dry a soil in hot weather, only because I use Kontos and it does get hot here, but for over 3 years I have been trying to figure it out and am still not close to the answer.

[Charlie]

David, the best way to know if it is spider mites is to visually confirm them. To do that you have to order a lighted loupe or magnifier that is in the 20x range. These are available at Amazon and all over the internet for not much money - $20 typical. Definitely get the lighted type. You can not only see the mites with these but even their eggs. If you cannot find mites with one of these then the problem lies elsewhere (although mites can do damage and then be killed by sprays and the visible damage continues to show up for many days after the mites are dead and gone).

Charlie

[davidwood]

Thanks Charlie, I have just ordered one on eBay. To be honest I had never heard of a lighted loupe and my magnifying glass is not much better than my glasses.