Friday, July 18, 2014

Identifying Bacterial Wilt in Cucumbers

Into every gardener's life a little tragedy must fall, and when you grow cucumbers, that tragedy usually takes the form of bacterial wilt.

I planted two entire packages of Burpee Pickler and Straight Eight cucumbers, my favorite varieties.  And, to my surprise, I had a really high germination rate.  Thus, I have cucumbers climbing my cucumber trellis, cucumbers under my sunroom windows, cucumbers on the terraced hillside that Mr. FC&G is excavating, and cucumbers in a grow box.  Those are the ones you see to the right in the photo.

Bacterial wilt is an insidious disease spread by cucumber beetles.  If you've never seen such a beetle, you're in for a treat, at least initially.  They are simply the prettiest bugs ever; they look like something that should have been dreamed up by Willy Wonka, with their neon yellow bodies decorated by precise black stripes or dots.  Really, these things look too perfect to be bugs.

Trust me, they are.  They harbor a bacterium in their systems when they are waiting to emerge in the spring, and when they come out to mate and feed, they chew on the stems and leaves of your curcubits (including cucumbers) and inject the bacteria.  Once the plant has caught the bacteria, the water transportation system inside the stems and leaves gradually shuts down, leaving a plant that looks like the droopy one in the photo. There is no cure; I'll be removing this plant this weekend.  The other plants in this box are probably fine; at least; I hope they are.

Since there's no cure for wilt, gardeners are left to guess if their plant is infected until it makes itself evident. Sometimes, a few leaves will wilt and I will panic, only to find the plant was eager for water.  That's always a good first diagnostic step, although it is not 100 percent on identifying wilt.

I knew I'd have to deal with a little of this scourge because I had an absolute flock of cucumber beetles emerge over the Fourth of July.  I went outside to the garden about once an hour during the morning and evening (when they are most active) and pinched them off the flowers, where they were sitting and mating, of all things.  The nerve of them!  I hope they enjoyed it, because it was the last thing they'll ever do. Nonetheless, I couldn't get all of them, so it was inevitable I'd lose a few vines to wilt.

I installed some yellow sticky traps and used some insecticidal soap spray for control, and now I'm only seeing one or two beetles on a plant a week.  This fall, I'll probably spray with beneficial nematodes, which help control the cucumber beetle larvae.

In the meantime, the only thing to do is make sure I don't spread the wilt myself.  That means being careful about not touching other plants or harvesting with hands that have handled wilted plants or that have squished bugs, and disposing of wilted plants some place other than compost.
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