My No. 1 Tip for Dealing with Corn Rootworm Beetle


If you look at some of my previous posts, you can I tell I love dahlias. They’re the first flower I ever grew on my own but I lived in a different time zone at the time.  To say that gardening conditions changed when I moved from zone 7B to 4B is an understatement. I basically had to go back and learn all over again. I became a gardening rookie at that point.  

From choosing what plants I love (goodbye jasmine, hello peonies) to dealing with extreme weather, I had to learn what worked in this growing zone.  But without a doubt, the biggest pain has been pests especially those afflicting dahlias.  Enter my nemesis—the Northern Corn Rootworm Beetle.

The next few photos shows you just what kind of damage they can create.  For more on this pesky little damager, click HERE. But the bottom line is that these tiny green beetles are very damaging. Before I even knew what they were I noticed that they only attacked light colored dahlias-- so there went Café au Lait, Iceberg and Center Court dahlias.  Below you see the Center Court and Iceberg, and how the beetles just destroyed them.  It is heartbreaking to get a tuber to bloom only to have the flowers destroyed.


Corn rootworm beetles go from corn fields (can be a crop field where corn has been planted in the past) usually around mid-late summer and they feed on flowers and vegetables. They seem most attracted to light colored flowers such as dahlias, roses, and others. Even small numbers of beetles can ruin flowers by feeding on the moist buds or petals. 


I have tried everything under the sun to rid my plants from these beetles and nothing has worked.  From neem oil to natural/organic chrysanthemum powder... nothing. At one point (I am not proud to admit it) I used a pesticide but I could not keep doing it. I have worked really hard to bring back pollinators to our garden area and this would be disastrous. And even then, the pesticide did not killed the nasty critters! Then my tubers supplier and I had a conversation and she let me in on a pro tip that she uses in her cut flower business-- organza bags. 

I know what you are thinking since I probably thought it. Organza bags seems pretty “out there” but she swears by it especially for the younger buds, and it is when the dahlias are at this tender stage that the beetles seem most attracted to them.  So I tried it.  And guess what? They are working like a charm.

Look at the near perfect petals of ‘Penhill Watermelon’ which just started opening a few days ago, and ‘Breakout’?! 

I also have a slug problem, so I used some diatomaceous earth on the leaves of the dahlias.

I also have a slug problem, so I used some diatomaceous earth on the leaves of the dahlias.

The thing about organza bags is that they may be too small as the buds bloom open, so I have various sizes-- 8x12 for dinnerplates, 5x9 for decoratives and pom poms.  Seems like an odd thing to do but it does provide a barrier against the pesky guys especially if you do not want to use pesticides.

One thing I have been reading about are nematodes, and their effectiveness against the beetles.  I hear they are effective but the beetles reproduce quicker than the nematodes can take care of them.  Still, for now it is an option in my pocket.

Do you have beetles in your garden? Have they destroyed any of your plants?

There is change you can find me in these link-up by other fantastic plant lovers: August Garden Party, In a Vase on Monday, Mosaic Monday, Garden Blogger's Bloom Day (15th of the Month), Home Sweet Home, Floral Bliss, Home and Garden Thursday, End of Month View(31st of the Month), Harvest Monday, Blooming Friday, #MyGloriousGardens, Gardens Galore, Six on Saturday, Pink Saturday, Sundays At Home, The Gardener of Eden, Flaunt Your Flowers/Fertilizer Fridays with Tootsie Time