Colocasia: Water soaked spots, orange spots, & black bugs

Lady's Island, SC(Zone 8b)

I have several Colocasia Black Beauty pups I brought inside for the winter. (However, our winter has been so mild that I could have left them outside). Anyway, they have been growing really good in my bathroom which gets good sun for about 3 hours in the early part of the day. I also run a humidifier in there for several hours a day a few days a week. The soil is moist, but not soaked.

So I have 4 problems I need help with:

1) (Pics 1 & 2) About a week ago, I noticed one of my Colocasia Black Beauty was getting some soft, almost water soaked looking spots on, the edges of a leaf, but otherwise appeared healthy and was growing great and putting out a new leaf about once every 2 weeks. These areas are becoming transparent, though. All the research I found with this description mentioned Leaf Blight, but none of the pictures looked anything like the issue with my Colocasia.

2) (Pic 3) Then I noticed that another one of my Black Beauty was developing some orange-brownish areas on the edges of its leaves. When I researched the potential cause for this, one website mentioned the spots could be due to lack of Phosphorus. Because the plants were babies (4-5 inches tall) when I potted them up, I hadn't yet fertilized them. So, I thought, ok, maybe that is the problem, but I do not know for sure.

3) (Pic 4) I also have a Colocasia Fontanessii that has been growing in a pot since July. I received it from the local garden center when they were cutting the pups off their mother plant by their pond. It took awhile, but it is looking good and now about 3 feet tall with 3 leaves and another one on the way. All is well, except for some brown leaf tips. I can not find a cause for this as it is supplied good humidity and water. Thoughts?

4) Ok, so I am an avid plant pest hunter and inspector...inspecting the plants all over...sometimes as much as 3 times a day LOL Yeah, I'm paranoid. However, it paid off. A few days ago, during an inspection, I noticed minuscule black dots, or perhaps they are brown, on the under side of the leaves on just about all of my Colocasia. These dots are the size of a period (.) or perhaps even a little smaller, however, because I inspect so much, I know these dots don't belong there. So, I gentle brushed one onto my finger, pressed against it with my thumb, and a little bit of liquid came out of it. So, I knew it was a pest and not a dust particle or dirt. There were only about 3 to 6 of these bugs on the underside of the leaves. Some leaves only had one or two. The bugs are easy to wipe off or spray off with the shower head, both of which I did to all of my plants. Later that night, after the leaves had dried, I inspected for the black dots and found none. 2 days later, I started finding them again, 2 or 3 on some, not all, of my plants' leaves.

Now I have seen aphids before on my Hibiscus this past summer and these looking nothing like them. There is NO webbing anywhere on my Colocasia...not at the base of the stems, not along the stems, nor under the leaves. But other than these 2 pests, I don't know what else it would be. These black dots weren't seen in the same area of a leaf, but more like one near the tip, another near the bottom, and 1 or 2 around the center. They didn't appear to be moving to the naked eye...just kind of there like a speck of black dust, except they ooze when you squish them. I don't have a picture of them as I wiped down each leaf and sprayed horticulture oil this morning. I think they'd be too small to show up in a picture anyway.

Hope someone here can help me with these issues.


Thumbnail by SavvyDaze Thumbnail by SavvyDaze Thumbnail by SavvyDaze Thumbnail by SavvyDaze
Clermont, FL(Zone 9a)

Maybe a nursery that specializes in aquatic plants could help you. Mine get like that every time a leaf falls below water level in my pond and eventually I have to cut it off. Fish nibble it too. Mine is a black magic and does keep putting out new growth but it is in a pond in a depth right up to top of pot. I should climb in and raise it to protect it from the koi I guess. When the water warms up more I will.

Hope you can find out what is causing aphids on your leaves. I'm surprised considering its inside.


Dublin, CA(Zone 9a)

Tiny black/brown dots on the underside of leaves sounds like spider mites to me, but if there were only a couple of them it sounds like you caught them quickly. Make sure you keep your eye out for them--if you catch them early you can generally just wash them off the leaves, but if you let the infestation get bad then you may need harsher measures. They spread very easily to other plants so if you had anything else near these plants I'd check them too. Webbing can be associated with spider mites, but I think it normally only shows up if it's a bad infestation. I've always caught things in time before they got to that stage.

Lady's Island, SC(Zone 8b)

Bonnie, would that mean I am watering them too much? Mine are potted and not hanging down in a pond lol

Ecrane, I had a feeling that is what it is. Since spraying horticulture oil yesterday, I didn't see any today on the leaves. Weird how it would be spider mites with all the humidity and misting I do to them. Oh well....I'll just be diligent about keeping them away.


Contra Costa County, CA(Zone 9b)

I wonder if you are not allowing the water to run through the soil enough.
Normally these are water plants, so any salts in the soil are quickly diluted. But when they are overwintered, not in a pond, whatever fertilizer is in the soil might be responsible for the brown tips and edges of the leaves.

Suggestion: If your water has minerals or salts in it, then use distilled or reverse osmosis water and leach out whatever might be in the soil once in a while.

In the mean time, use some slow release organic fertilizer, not a man-made product that is more of a salt.

Lady's Island, SC(Zone 8b)

My soil is mixed with orchid bark, vermiculite, and Miracle grow Organic Potting Mix. When I water, I let it run out of the bottom, and with this mix, it seems to do so fairly quickly. I also let the water sit in the tray for an hour or so before I empty just enough out to barely cover the rocks in the tray. The Colocasia Fontanessii and one of the Black Beauty are in self watering pots, the others are in clay pots, and those are the ones in the pebble trays. The ones in clay pots are watered every other day as they are only 6 inch pots and dry quickly.

I was thinking that sometimes I do sit some of these on the window sills, where sometimes they remain overnight, and am wondering if the coldness of the windows might be causing the brown edges. For precautionary measures, I have moved them 10 inches away from windows as of yesterday.

Also, how much sun do these Colocasia need inside at this time? I have read to give them full sun in southern or western windows, just morning sun from an eastern windows, and even read to keep them 7 feet away from a window in indirect sunlight. So, I am a bit confused about lighting LOL

Contra Costa County, CA(Zone 9b)

In the winter there are so many cloudy days that even southern exposure is probably not too much.
You are right that the icy cold where the leaves were touching the windows can cause damage. good that you moved them back a bit.

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