Battling Blister Beetles: A Tale of False Indigo and Alfalfa

Who knew that false indigo (Baptisia) and alfalfa had a common enemy? Not me, that is until recently when I had an encounter with Epicautafabricii, more commonly known as the ash-gray blister beetle.

Picture this: It’s a quiet Saturday morning, and my husband and I are sitting down, happily munching on toast and sipping our coffee. I happened to glance out the dining room window, and my eyes must have gotten huge because my husband looked at me and said, “What’s wrong?” I responded, “I’m not sure, but my false indigos have no leaves!”

Naturally, I had to investigate. The plants – five of them – were all fine yesterday. What I saw made my skin crawl. Hundreds of blister beetles! Blister beetles are native to many parts of the U.S. and ranchers are no strangers to these troublemakers. They can wreak havoc on alfalfa crops and pose a serious threat to livestock.

That’s because the beetles carry a nasty chemical called “cantharidin” in their bodies. If animals or humans accidentally ingest them, it can lead to all sorts of urinary and intestinal issues. In fact, even a small number of blister beetles — around 30 to 50 — in alfalfa hay can be fatal to a horse! And while we’re not sure about the toxicity levels for cattle, it’s known to cause mouth sores. Oh, and here’s the kicker — just coming into contact with these beetles can give you blisters on your skin! You can check out this NDSU Extension news release for more info.

Usually blister beetle problems get worse when the weather is dry. But last fall, we had an unexpected pile of snow hit before the ground froze. Turns out, that probably helped protect the beetle larvae or something.

We live in a development far away from any alfalfa fields, so having a beetle problem in our yard was a real surprise. But as I dug deeper into these beetles’ preferences, I discovered that they’re also quite fond of sweet clover, which just happens to grow abundantly in nearby ditches. So that might have been part of the reason they showed up. And get this — ash-gray blister beetles are immune to the protective alkaloids in Baptisia that usually keep other insects away.

Once I identified the culprits, I knew I had to get rid of them. I read some advice on a garden website suggesting manual removal of the beetles. Can you imagine? Squishing hundreds of beetles one by one? No thanks! So, I went with the chemical solution instead. I found an insecticide, gave it one good dose, and guess what? The lone surviving Baptisia at the other end of my flower bed was saved!

But more worrisome to me — I saw a post on social media from western North Dakota, and it seems blister beetles are becoming a problem there. I genuinely hope that as ranchers in the state cut their alfalfa, they won’t have to face the same issues I did. The potential losses for them are heartbreaking. Losing an entire alfalfa crop or unknowingly feeding contaminated hay to their animals — that’s a nightmare scenario.

So, to all the ranchers out there battling blister beetles, I’m rooting for you! May your crops be beetle-free and your livestock safe from these pesky bugs. Hang in there, folks!

Dawn Smith-Pfeifer is content and communications director at North Dakota Farm Bureau. This column was originally published by NDFB and is republished with permission.