Of course my first thought was, “What the heck are cucumber beetles doing eating my dahlias?” particularly when my cucumbers seem to be unaffected.
After doing a little digging, it appears that they don’t have a problem eating flowers and can be found on the flowers of many ornamental plants. Why this picked this dahlia to harass, I have no idea.
There is some good news. Spotted cucumber beetles (unlike their trendy striped cousins) do not overwinter here. Apparently the adults fly up from the south in mid-summer, lay their eggs in weedy or grassy areas where the larvae hang out until it gets dry and then they fly off to terrorize gardens. We’ve had a very wet summer until the past very dry few weeks, so the timing seems to make sense.
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| They even seem to have settled in on a new bud, waiting to lay waste to my beautiful flowers. |
In terms of controlling them, none of the options seem particularly useful or helpful. Handpicking is mentioned as an option, and I have no problem with that as I’ve been squishing sawfly larvae and handpicking Japanese beetles all summer, but I just don’t get how that works when the things fly away as soon as I get close. Putting out sticky insect-catching tape by itself or lining the inside of a plastic cup (I knew Red Solo cups would make their way into gardens soon enough, as they seem to have infiltrated every other aspect of society) and perching it upside down on a stake are also said to be options for catching them.
Everything else involves pretty nasty non-selective insecticides that I’m not interested in using in my garden.
To be honest, there’s not much chance of saving these dahlias at this point. I could cut them back and maybe get one more bloom out of them if I could get rid of the beetles, but so far that seems unlikely. Soon enough the beetles will either die or move on, and hopefully not in my yard, and the problem will solve itself.
Just one more new challenge in the garden.
More reading on managing spotted cucumber beetles:
University of Minnesota Extension
University of Maryland Extension
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I hope to not run into this pest. Thanks for the information.
I wonder if an essential oil would work? Usually peppermint oil (diluted in water) keeps away insects. How many of these plants you have might be an issue though.
You are right that it is always something new. This year for me it's the worms, Jp. beetles that I did not discover until they consumed a new rose and an old willow shrub, some wormy thing on a little birch tree and the tent caterpillars. Did not get sawfly on the pines for the first time in years. Am I leaving anything out. Sometimes you feel like you are spending all your time attacking weeds and critters which makes it hard to enjoy the garden.
You could put plastic bags over the dahlias, the cut the dahlias, trapping whatever insects are inside the bags, then tying the bags and throwing them in the garden. It is interesting as I've had problems with the Japanese lily beetle. I don't know why but the only thing different is that I put a pine/spruce wood mulch on the ground last year. Maybe the larvae can't survive the resins while climbing through it in the spring. Obviously not a total solution as the invaders can fly in from other gardens but still interesting. Good luck with yours.
that should be throwing them in the garbage, not garden. Also add a line It is interesting as I've had problems with the Japanese lily beetle until this summer.
too early in the morning for me!
Cucumber beetles have been ruining my Cosmos and mums for the past week. I've never seen this issue before. (I'm in Virginia, by the way.) They go for the white Cosmos and not the yellow. I've been squashing them by hand every morning and evening and there are always more. *sigh* Every flower is quickly ruined after it opens.
The weird thing is, I can remember having horrible problems with Japanese beetles decades ago. Hanging traps, emptying out hundreds, thousands of dead bugs. I used them for mulch until my dog started eating them.
I haven't seen a Japanese beetle in years.
Donna
This is happening with my dahlias this year (in Colorado). Did they come back the next year?https://photos.app.goo.gl/VkZCHHe5r8hqy8ij6
Yes, I dug them and stored them along with all my other dahlias and they were fine.