Invasion of Black Blister Beetles

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By Joan Pritchard | Jul 26, 2016

I have had a few insect problems in my flower and herb garden over the years. For several years, grasshoppers attacked, eating any and everything green and even ate the bark off the small trees. Although I have not seen black blister beetles for several years, this year they have arrived and are doing great damage.


Blister beetles will feed on just about any leaf that grows in your garden. They have now removed the chard from the garden and are starting on my hostas. They seem particularly fond of certain weeds that grow in the pathways. The experts tell us they can arrive in swarms, and indeed, they do seem to have done so. 

The one redeeming quality of black blister beetles is that they also do damage to grasshoppers, one of the most destructive farm and garden pests. “Newly hatched beetle larvae use their legs to seek out clusters of grasshopper eggs to feed on. In this sense, blister beetles can be considered a beneficial insect, but only in the larval stage. Once they become adults, they’re nothing but trouble” (PlanetNatural.com).


Planet Natural has a comprehensive list for control of blister beetles which I have abbreviated below with comments:

• I should have been more observant earlier, but I was so busy trying to control Johnson grass that I overlooked insects. Planet Natural recommends “frequent and careful inspection of home gardens. The numbers increase gradually in the growing season’s early months, and an observant gardener can keep them from doing much damage.”

• I am not sure I approached the problem in the correct way, as I donned rubber gloves and hand-picked the beetles, then stomped them. Planet Natural recommends to “never handle blister beetles with bare hands. Always wear gloves. Brush the beetles off plants into a small container with some soapy water. If shaken from plants, the beetles will often lie in the dirt and play possum rather than scurry away. Take advantage and gather them carefully.”

• I noticed some plants attract black beetles – plants I would call weeds. One of their favorite plants turns out to be pig weed, which I don’t have a lot of, but it must be enough to attract. Planet Natural suggests we keep grass, weeds, and other growth trimmed around the margins of the garden to remove the places where they might get started. I am doing this, so hopefully I can get these guys under control.

• I haven’t tried row covers, but I’m ready to try them now. Plant Natural suggests that “Well-anchored row covers can keep migrating beetles off your plants in the mid to late summer. They will not stop early season adults who over-winter as late stage larvae in the soil. Use them if you notice clusters of beetles (or expect them) in and around your garden come July.”

• Turns out that while blister bugs attack grasshoppers, they are also attracted to them. With the invasions I have had of grasshoppers in past years, I may have to work particularly hard to get rid of the blister beetles.

Always a problem on the old homestead isn’t there?  It certainly makes life interesting.

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