Identify and Treat Plant Problem

Asked January 20, 2013, 2:00 PM EST

I have an Ipomoea batatas ‘Blackie’ plant in a container with a couple other plants. It's just the Ipomoea that is having any problems. I've looked high and low to identify the problem, but don't see anything that fits. I'm attaching a picture of a leaf with the problem; but briefly, new leave quickly shoot up from the stem and within a few days develop tiny, bunched spots mainly along the veins of the leaf. The leaf then shrivels up within a couple days and falls off. I really like the plant, so if there's a way to fix this I'd like to know!

Thanks,

Daniel Kelber
Any ideas? I thought someone was supposed to get back to me within 2-3 days.

Cook County Illinois disease issues plant disease horticulture

4 Responses

Hi Daniel --

Your question was just assigned to me, so I can't explain the delay, but I hope I can explain those spotty Blackie leaves!

First, kudos for trying to "winter over" Ipomoea batatas -- easy as they are to grow outside in a container over summer, they aren't always easy to keep happy when confined indoors! They can be finicky about conditions, and are quite susceptible to pests -- white flies, mites, thrips -- which they shake off far better in the sunny outdoors, sometimes with a little help in the form of a blast from the garden hose.

The good news is that, from the photo, I'm going to guess that the problem is not insects. (I say "guess" because the picture is a bit fuzzy, and you'd need a special lens to get up close enough to get a sharp shot of little dots on leaves!) This looks like a case of oedema (otherwise spelled edema), which is a physiological disorder rather than a "disease" caused by a pathogen or pest.

Oedema occurs when the uptake of water exceeds a plant's ability to properly absorb that water, and the result is rupture of cells that can show as spotty "water blisters". As the cells "explode", tissue dies and, given sufficient damage, the leaf will shrivel, die and fall away. I'm not surprised you didn't readily find recognizable information on oedema: Plants vary in their susceptibility and presentation, but in general it's not a widespread problem in ornamental plants. Because oedema is a reaction to environmental conditions, most growing guides or fact sheets focus on describing cultural requirements that would prevent the syndrome from appearing. When you do see the condition mentioned, it's usually in the context of vegetables (it can be a problem with tomatoes), or in commercial production of ornamentals.

Here's an article from the University of Connecticut extension that discusses oedema. A common victim in the greenhouse, and primary plant discussed in the article, is ivy geranium, but the advice (including how to differentiate oedema from insects!) applies to your sweet potato. There also happens to be a photo link (#2) that shows oedema on 'Blackie'. Take a look:

http://www.hort.uconn.edu/ipm/greenhs/htms/edema.htm

As the article notes under "prevention", your strategy should be to make sure you're not "out-watering" the plant's ability to use the moisture it receives. It looks like at least one of your sweet potato's pot-mates is a Coleus, so you might turn that pot to get both toward the sun, too. As a bonus, more sun may help reduce sunburn if you intend to move them outside when weather permits!

Thank you!

You're welcome! Forgive me if you're an avid outside gardener and already know this, but: In case you're not able to get the oedema under control, know that come mid-May, I. batatas 'Blackie' (along with several other attractive cousins) will be widely available at garden stores as an accent plant for outdoor containers. Enjoy!

I've got a pretty black thumb, so thank you for all your advice. I have a feeling I'll be getting some more blackies come spring!

Daniel