Jujube disease?

[alliumnate]

One of the things that got me interested in jujube was observing a couple of jujube trees at work that produced reliably over the course of 10 years without any pesticide applications and regardless of whatever weather conditions the trees were exposed to during the growing season. I figured that jujube might be an ideal fruit for a no-spray in our area (TN, zone 7a).

However, I noticed some disease symptoms on my sugarcane jujube last year. And the symptoms this year are even a bit worse. The particular tree showing symptoms is in its 4th season in the ground. Last year, was my 1st harvest, with the tree producing about 40 fruits. This year, I can only find 5 fruit on the tree!

What I’m seeing are grayish-brown lesions (often circular rings) on leaves starting in June, leading to partial defoliation of the tree by August. My best guess is Alternaria. But there’s little information that I can find about fungal diseases in jujube (particularly in the US).

The last two years we’ve had unusually dry May and early June conditions, followed by wet late June and July weather. We’ve actually had fewer inches of rain this year, despite having more days with rain. So it’s been wetter in that sense.

Here are some photos of what I’m seeing:

FYI - I’m also growing Li, Lang, Honeyjar, Shanxi Li, Norris, GA 866, and TY Yazoo Li. But I have only observed the symptoms on Sugarcane. I’m not sure if that’s because Sugarcane is more susceptible, or if its just the first to get it before it spreads to other cultivars in the coming years. I don’t think it’s due to micro-climatic issues with this particular planting site. Other jujubes are fairly close by in proximity, and receive the same amount of light, water, airflow, etc.

Has anyone else seen similar symptoms on jujube? If so, have they been specific to certain cultivars?

Any thoughts?

[mamuang]

This is concerning.

Most of us switching to grow jujubes because it is supposed to be low maintenance fruit tree.

Let’s see what @jujubemulberry , @BobVance , @castanea , @k8tpayaso, @tonyOmahaz5, et al, say and if they have experienced such issues before.

[alliumnate]

I’m not sure how concerned we should be. I’ve got 8 planted jujubes in the same general area and a dozen or so close by in containers. And this sugarcane tree is the only one that’s showed symptoms. I’ve also propagated a bunch of rooted cuttings and grafts from this tree, and haven’t observed symptoms in any of those. So this one is definitely atypical…at least for now.

Thanks for tagging our resident jujube experts! I’m curious to hear their thoughts.

[castanea]

Never seen that but I’ve seen similar problems on other fruit trees.
Where is this growing?

[alliumnate]

Middle Tennessee area. Zone 7a.

[rubus_chief]

I also think it is a fungal leaf spot and could be Alternaria based on the size in the 1st pic and the timing of symptoms appear similar (starting rapidly in June and defoliation in August)

Per CA extension:

it is found on almonds in the US when hot and wet and their pic; their model is temperature x duration of wetness on the leaf (so both high temps and long duration of wetness on leaf increases severity)

It is also common in broccoli and cauliflower

Symptoms and Signs

Alternaria leaf spot appears as fairly large brown spots on leaves, about 0.5 to 0.75 inches (12–18 mm) in diameter. The spots turn black as the fungus produces spores. Leaf spot develops most rapidly in June and July, and trees can be almost completely defoliated by early summer when the disease is severe. The disease appears to be most severe where dew forms, humidity is high, and air is stagnant.

Another pic on Brassica per MN extension

“However, heavy infections of foliage can reduce plant vigor and can result in lower than expected yield”

I have a Honey Jar and Sugar Cane and we have wet summers so curious about this

[k8tpayaso]

I have not seen this. Our weather is wet and hot in early spring and hot and dry in late spring/summer. I haven’t seen it on other plants either.

[rubus_chief]

Do you think this started on the fruit and overwintered in the soil? And now has spread to the entire tree?

Or do you have crops nearby where Alternaria is more common (melons, cabbage, broccoli, etc)? Or is this the only occurrence specific to jujubes?

Was there anything about your weather last year that was usually wet or very hot and wet?

There are a lot of anti fungals recommended for Alternaria (or Cercospora or some other fungal) but I wonder if 1% hydrogen peroxide is a more simple less drastic solution.

[jujubemulberry]

sorry for delayed response… Anyway, am inclined to agree with @rubus_chief
though have to say am not really the expert on this as never experienced this in our low-humidity locale(las vegas).

if it was a type of sap-sucking insect that did it, it is possible the culprit prefers sugar cane to other varieties, strange that might sound.
i say this because have witnessed preferential attacks on the cultivar bok jo by leaf cutter bees . Sugar cane and chico seem to be 2nd and 3rd in preference by leaf-cutter bees.

we also have a sihong seedling that grasshoppers seem to prefer nibbling on, leaving other cultivars untouched.

anyway OP’s tree would make a great case-study if it survives the malady, and whether or not it continues to present same symptoms on next spring’s leafing out.

we’ve had several cultivars that exhibited sickly buds/stems/leaves one year, then never again on succeeding years which make me think the species is capable of developing some sort of immunity, or perhaps decrease in susceptibility as the trees mature.

am hoping with some optimism your sugar cane will do the same-- pls keep everyone here posted

[Podunk]

I’m in northeast Arkansas. I’ve got a Li jujube (planted last season) with lots of leaf spots that look different from those posted above. There is no defoliation. Any thoughts?

[castanea]

I see those on various plants. I don’t know what they are but they look more like damage from an airborne toxin than a disease.

[rubus_chief]

That looks like Cercospora leaf spot - another fungal leaf spot disease