Last summer about this same time I was horrified when I saw hundreds of awful gray bugs- blister beetles- all over my beets. They covered the foliage, eating everything. I can handle insect damage to some degree a couple of nibbles here and there that dont kill the plant are within an acceptable range but I knew this would wipe out my entire crop.

Beetles That Leave a Blister

I found out they were blister beetles, and I’m glad I didnt automatically pick them off by hand since they produce a toxin that can blister the skin. As a matter of fact, when blister beetles infest alfalfa fields (one of their preferences) they can cause severe problems for livestock, including death for horses, who ingest the insects when theyre caught up in the hay.

The chemical, cantharidin, remains stable even after the beetles are killed making infestation a serious problem for hay growers. Touching them in the garden can result in blisters on your hands or arms so you have to be careful picking them off by hand.

There are over 1,000 varieties of blister beetles throughout the United States, and many times they travel in swarms. This is why they suddenly appeared on my beet greens. Typically, the females lay eggs late in the summer that overwinter in the ground. When the larvae emerge, it will often feed on grasshopper eggs, which is why some consider these beetles a beneficial insect. I guess it depends which one you want chewing on your veggies! Personally, Ill take the grasshoppers.

How to Kill Blister Beetles

When I figured out what they were, I learned I could douse them with Neem oil or pyrethrum since I prefer the less toxic route. Of course, the old stand-by, Sevin, works as well. Since I was pregnant and miserable last summer, the thought of hauling our not-always-cooperative toddler, Samuel, into town to pick up a spray was the last thing I wanted to do. A potentially screaming one-year old seemed worse than beetles devouring the garden.

I initially tried drowning them by hosing them off the greens with the hose, but of course, they simply fell to the ground and crawled back up the stalks. Then I pulled out the Shop-Vac. That did the trick. I sucked up the nasty little devils, and sent them to beetle oblivion. I put the hose over the whole plant to make sure I got as many as possible, but still had to vacuum them off one more time after the initial “sweep” since a few escaped.

Since then, weve had no problems. My guess is they came in from the nearby alfalfa fields, which is where I hope they stay this season. Im confident they werent here long enough to lay eggs, but am keeping a vigilant eye on our precious beets (which won Samuel a blue ribbon at the state fair this year!) so I have enough to pickle at the end of the month.