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A nearly sudden wilting and browning of cucumber plants is likely a case of bacterial wilt spread by beetles.
(George Weigel)
Q: I have a small garden in my backyard where I plant tomatoes, bell peppers and cucumbers. For the past three years - even with new soil - I have experienced blight on all three. My immediate problem and question is with the cucumbers. They were doing fine and now are all wilting, getting holes in, then dying. Can this be from the soil or from critters in the soil?
A: I think we're all in for a worse-than-usual disease season because of all the rain we've had lately. Warm temperatures, high humidity and frequent wetting of leaves is the perfect storm for blights and leaf-spotting.
I'm already seeing both early blight and septoria leaf spot on my tomato plants. I wrote a Q&A last summer on what to do about those.
As for your dying cucumbers, that's most likely bacterial wilt (which I'm also seeing on some of my cucumber plants).
The striped cucumber beetle is a leading way that bacterial wilt is spread.
This particular disease is a bit different than most veggie diseases because it's caused by a bacteria and not a fungus. It's also almost always spread by spotted and striped cucumber beetles and so isn't as weather-related as diseases such as tomato blight and powdery mildew.
Cantalopes, pumpkins and squash also can get bacterial wilt, although not as readily as cucumbers.
Cucumber beetles are very common early-summer garden bugs in our area. They're less than half the size of Japanese beetles and somewhat elongated hard-shelled bugs with either yellow spots or yellow stripes.
Since the beetles spread the disease, if you stop them, you stop the wilting. Once the plants wilt, though, they're done. They usually die a pretty fast death at that point.
Spray-oriented gardeners usually use either carbaryl (Sevin) or a combination of rotenone and pyrethrum to kill cuke beetles. You might need to spray every 10 to 14 days while they're active.
I'd rather not spray any more than absolutely necessary, so I try to solve the problem by successive planting, which means planting small crops every couple of weeks instead of planting everything all at once.
What happens is that I usually get a picking before the wilt kills the plants, but then my next crop comes along a couple of weeks later. I'll get fruits off of those for a little while until wilt gets them. Then my latest plantings usually avoid the disease because they mature after the beetles are done for the season.
Some cuke varieties are more resistant to the beetles and the disease than others, so switching to a different variety next year might help.
This year, for example, I've already lost nearly my entire planting of 'Telegraph Improved' cukes to wilt, while a planting of 'General Lee' a few feet away is producing nicely with no sign of trouble (yet).
Other varieties that I've seen touted as wilt-resistant are 'Marketmore 76,' 'Saladin,' 'County Fair,' 'Eureka' and 'Calypso.'
Yellow sticky cards are a way to trap cucumber beetles.
Another option is covering the plants with floating row cover, which is a light-weight, spun-bonded fabric that lets rain and most sunlight through but creates a barrier for flying insects. The catch is that you have to remove the cover when the flowers come out to allow bees to pollinate the flowers (unless you're growing a self-pollinating type of cucumber, such as 'Diva' or 'Sweet Success'). Once the cover's off, it's a race between the beetles and mature cukes.
One other trick to try is stapling a few sticky yellow (or yellow-spray-painted) plastic cups to stakes. Coat them with a goo such as petroleum jelly or Tangle Trap. The yellow color attracts the beetles, and the goo captures them like a fly trap.