Blister beetle infestation on Lupine - Ask Extension
I have a fairly large planting of Lupine in a praire at my cabin in Pine county. We discovered an infestation of black blister beetles on them (hundr...
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Blister beetle infestation on Lupine #331712
Asked June 12, 2016, 10:56 PM EDT
I have a fairly large planting of Lupine in a praire at my cabin in Pine county. We discovered an infestation of black blister beetles on them (hundreds of them). They are eating the blossoms and stems and are also eating the Baptisia. Is there anything I can do? I would prefer not to use an insecticide that will also kill good bugs. Also, will they attack other plants - garden, or crops?
Pine County Minnesota
Expert Response
Hello,
Blister beetles can form large aggregations, like the one you are experiencing. The infestations of adults usually dissipate after several days. However, new aggregations may appear in other locations over the summer.
The immature stages are beneficial in that most species prey on grasshopper eggs or other insects. The species in your picture looks like it may be in the genus Lytta (just in case you're curious). The immature stages of these attack ground nesting bees, like bumble bees and other species.
It is just the adult stage that is damaging to plants. They seem to have fondness for legumes so it is not surprising to seem them on lupine and Baptisia. Blister beetles can feed on a number of other garden plants (including tomatoes and potatoes, etc.), so keep an eye out for aggregations appearing elsewhere. There is typically one generation a year with adults most common in mid summer (June - August, depending on geographic location).
As for management:
If the infestation is limited to just a few plants, you can knock the beetles off the plants into a bucket of soapy water, or pick them off and drop them in the soapy water. They are called blister beetles for a reason - their bodies contain chemicals that will cause skin blisters. Blistering depends on the species of beetle and the individual's sensitivity. Just to be safe, please wear rubber gloves when handling them. (Don't use your regular garden gloves as they may absorb some of the chemicals into the leather / cloth).
For a more widespread infestation, like you seem to be experiencing, you can use insecticides containing neem oil or azadirachtin (a component of neem oil). These materials generally safe for beneficial insects, including bees. Different brand products of these materials are available at most garden supply stores. Other insecticides may also be effective on teh beetles, but they are potentially more toxic to beneficial insects. As with any pesticide, please follow the directions on the label carefully.
You can do spot treatments - applying the insecticide to plants that are infested. To further minimize any potential effects on bees, you can apply the insecticide in the evening after the bees are not foraging.
Blister beetles can form large aggregations, like the one you are experiencing. The infestations of adults usually dissipate after several days. However, new aggregations may appear in other locations over the summer.
The immature stages are beneficial in that most species prey on grasshopper eggs or other insects. The species in your picture looks like it may be in the genus Lytta (just in case you're curious). The immature stages of these attack ground nesting bees, like bumble bees and other species.
It is just the adult stage that is damaging to plants. They seem to have fondness for legumes so it is not surprising to seem them on lupine and Baptisia. Blister beetles can feed on a number of other garden plants (including tomatoes and potatoes, etc.), so keep an eye out for aggregations appearing elsewhere. There is typically one generation a year with adults most common in mid summer (June - August, depending on geographic location).
As for management:
If the infestation is limited to just a few plants, you can knock the beetles off the plants into a bucket of soapy water, or pick them off and drop them in the soapy water. They are called blister beetles for a reason - their bodies contain chemicals that will cause skin blisters. Blistering depends on the species of beetle and the individual's sensitivity. Just to be safe, please wear rubber gloves when handling them. (Don't use your regular garden gloves as they may absorb some of the chemicals into the leather / cloth).
For a more widespread infestation, like you seem to be experiencing, you can use insecticides containing neem oil or azadirachtin (a component of neem oil). These materials generally safe for beneficial insects, including bees. Different brand products of these materials are available at most garden supply stores. Other insecticides may also be effective on teh beetles, but they are potentially more toxic to beneficial insects. As with any pesticide, please follow the directions on the label carefully.
You can do spot treatments - applying the insecticide to plants that are infested. To further minimize any potential effects on bees, you can apply the insecticide in the evening after the bees are not foraging.
