Every year it seems my cukes will go gang busters then suddenly the leaves turn yellow (starting with yellow spots), then turn brown, wilt and slowly die off. This all happens from the root crown and works its way out. I have pictures of early producing growth from about 2 weeks ago (mid-August 2014) and how they look now....Sept. 2 2014. The pictures may be most helpful. I see no insect activity, but I do have voles/moles in the area, but not every year. I live in Southwest PA, near Johnstown. Anything else I can answer please ask...Thanks Bill!

Update...planted in early June...the 2nd picture (should have been first) is the same plant about 3 weeks ago. I have added some pictures....yellow spots were scattered over the leaves but did not turn into holes and I see nothing that I think would be powdery mildew. This area is fairly wet, not the best drainage but it doesn't seem overly wet.

As an aside, what is that weed in the last few pictures? (My Mom called it the portulaca weed, don't know why), but I can't eradicate from my garden, seems to be self-rooting!

click any photo for full size

  • Hey, you're like 1 1/2 hours away. Have you seen anything unnatural near the base of the plant, where it goes into the ground? – J. Musser Sep 2 '14 at 22:42
  • Not on the one...but on the other something looks to have been gnawing on the stem at the ground line. The ground around either plant stem does not look disturbed. The stems themselves seem hardy. Been to a nursery with that name not far from Indiana. This is my first time on a forum like this, so not totally sure if I'm doing things correctly. – Bill Sep 2 '14 at 23:15
  • I'll have more time to answer later, but is the second picture a different plant from the one with the stem damage, or the same one earlier in the season? Also, can you post a picture of the gnawed part of the stem, so we can better diagnose your problem? I can go to my library and read all about cucumber problems, and find a match. None of my cukes have done that. It would also be good to know how fast that soil drains, and how much rain you've been getting. – J. Musser Sep 3 '14 at 3:50
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    And FYI, you've been 'doing things correctly' so far, in using this site, thanks for adding pictures, a location, and being descriptive. :) – J. Musser Sep 3 '14 at 4:00
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    See my updated info above and the new pictures...have not been getting unusual rain amounts lately and I seldom water them once they are established. – Bill Sep 4 '14 at 0:24
up vote 8 down vote accepted

I think you have Cucumber mosaic virus, because of the mosaicing, curling, and drying of the leaves, and the stop in production, plus the time frame of infection matches perfectly.

There is no cure. What you can do is try to keep it from spreading, which is done by removing affected plants from the environment. Burn or seal them in bags to prevent the virus spreading. Do not add to your composting system.

It is spread by any insect that feeds on cucumber family plants. When they land on an infected plant, and then land on another one, the disease will spread. I would suggest that you remove the affected plant immediately, and keep an eye on the remaining one. If the other one hasn't contracted the disease, yet, hopefully removing the mosaiced one will greatly decrease the likelihood of contraction. Another thing that reduces (but not eliminates) the chances of catching the virus is laying out an insect barrier early in the season. This keeps away most contact with virus carrying insects.

And the brown spots at the base of the stem appear to be corking, which is when an herbaceous plant builds up corky material on older stems when they increase in diameter.

Symptoms

Cucurbit plants may become infected at any stage of growth, from emergence of the seedling to near maturity. External symptoms may develop within four or five days after young plants become infected, but may take up to 14 days to develop when the foliage is older and more mature. Symptoms develop more rapidly at 79° to 89°F (26° to 32°C) than at 61° to 75°F (16° to 24°C). The severity of symptoms is at least partially related to the virus concentration. CMV symptoms in cucumber are more severe on plants exposed to short days or reduced light than on plants exposed to long days and bright light. Cucurbit plants rarely become infected in the seedling stage. When this happens, the cotyledons may turn yellow and wilt. New leaves are slightly mottled a yellowish green, remain small, wrinkled, and distorted. Plants infected in the seedling stage remain dwarfed or may die, and seldom produce fruit. Source

As for the weed you wondered about, that's purslane. Your mom was right, it is in the Portulaca family. It is edible and nutritious, albeit bad tasting to many.

  • That may well what it is, Thanks....actually both plants have it...so done for this season...just happy with what we did get! I will dispose of the plants and not compost them as I have in the past. Thanks for the tip on the insect barrier as well. I'll keep it in mind for next year. Any idea on the weed in the last few pictures?? – Bill Sep 4 '14 at 2:59
  • On the "weed" question...I think it is purslane...but I may have some spurge mixed in as well. But how do you prepare the purslane to eat? (My wife's not crazy about that though.) – Bill Sep 4 '14 at 19:08
  • @Bill I ate it raw. You can cook it like spinach (disgusting), but it won't shrink down like most greens. – J. Musser Sep 4 '14 at 21:04

I suspect an infection - what's important is the precise nature of the yellow spots when they appear - you've said it starts on the crown of the plant, which I take to mean the oldest leaves - if the spots are pale yellow, followed by grey fuzz or felt which might cover the leaves, it's powdery mildew. Left untreated, it will cause the results you show in some of your pictures.

If, though, the spots appear near leaf veins, roughly circular but not necessarily, and those 'spots' turn into holes, it's anthracnose, but there's no evidence of that from the pics.

Otherwise, scab is a possibility - the spots which you see initially are grey with a yellow halo.

The following might be useful to you

http://www.extension.umn.edu/garden/diagnose/plant/vegetable/cucumber/leavesspots.html

This answer assumes a contributory cause of the problem isn't lack of water.

UPDATE - I don't think it's any of the ones listing symptoms with holes in the leaves either, there aren't any holes to see in your pictures - more likely to be powdery mildew/drought than anything else on the list - dryness at the roots encourages powdery mildew. However, the extra pictures don't suggest typical powdery mildew either - what they do suggest is Downy Mildew rather than cucumber mosaic virus, there's no wrinkling, bubbling or torsion going on, which I'd normally expect to see with a virus.

So to sum up, I still think it's mildew - the one you get as a problem where you are is actually known as Downy Mildew, and it starts with this yellow patterning I can see on your added pics. Google Cucumber Downy Mildew and check the Images, or check out below:

http://www.cals.ncsu.edu/plantpath/extension/fact_sheets/Cucurbits_-_Downy_Mildew.htm

  • Bamboo, now I think it may be the Downy Mildew...mostly because none of our fruit had the warts associated with Cucumber mosaic virus...so many of these "illnesses" can look so similar to another! What do you think J Musser? This link was helpful to me: donnan.com/cucumbers.htm – Bill Sep 4 '14 at 19:04
  • @Bill Hmm, could have been downy, but when my cukes had downy mildew, they had spots like this. It doesn't cause the mottling as much, but does dry the leaves a lot more. So far, it seems the symptoms are mixed. I've had downy mildew, which I treated with copper fungicide, and successfully eradicated in a few days. Another thing, cucumber mosaic only grows warts on fruits that formed after the plant became infected. – J. Musser Sep 4 '14 at 21:02
  • I'll have to check fruit coming off now to those from earlier, if I have any left! True, my leaves never looked like the picture you provided. I think next year I need to plan to combat both these potential causes and see what happens. Now I how do I accept both your answers?? – Bill Sep 7 '14 at 2:05
  • @Bill I wouldn't worry about which one you accept from the vote point of view, its up to you, doesn't really matter. What does matter is if you think its mosaic virus, nothing you can do, but Downy Mildew can be treated if caught early next year... – Bamboo Sep 7 '14 at 14:18
  • @Bill If you accept, accept the post that helped you more. You don't have to, though, if you think it was rather unconclusive (I do). You could try treating for downy mildew, and see if that's right, if not, then it may be CMV. – J. Musser Sep 8 '14 at 19:52

I've also heard that cucumber plants can do this (yellowing/spotting of leaves) which can be caused by a magnesium deficiency and cured with Epsom salts. Here's a YouTube segment discussing this.

I live in Golden, Colorado and mine too interestingly began to have yellowing leaves and drying up recently (early September) as the author of this post. I have not tried anything on them yet and not sure it's worth it or if I would be able to bring them back at this point.

If this is still a problem, to help keep pests away, plant garlic nearby, but maybe not in the same bed(it can affect flavour in some plants I think? I don't really remember.. xD) also, using a yellow solo cups with Vaseline to catch aphids is something I'm trying this year!

Yes, it is cucumber downy mildew, which is a recurring problem in the eastern seaboard of the US. You can follow disease spread from this link http://cdm.ipmpipe.org/scripts/map.php and take preventative measures. We contribute to the monitoring of disease and provide most effective recommendations to cucurbit growers

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