How to Control the Blister Beetle

The toxin blister beetles carry may cause harm to livestock and humans.

Blister beetles are thin, elongated insects with large heads. They can be various colors from black to metallic and are about 1/2 to 1-inch in length. These insects are easy to identify because of their elongated necks. The blister beetle harbors a poisonous toxin called cantharidin which is emitted when the beetle is crushed or mishandled. The toxin causes blisters on human skin and sometimes gets crushed in with alfalfa and other animal feed making livestock very ill when they ingest it.

Things You'll Need

• Weed control options
• Grasshopper control options
• Insecticides

Instructions

Where Are They Coming From?

1. Know which type of blister beetle is affecting your area. Try to locate where the main source of the beetle is. Keep weeds, especially flowering ones like dandelions, cut back or eliminated and try to cut alfalfa fields before blooming starts.

2. Know when peak beetle activity occurs in your area. Harvest prior to high activity or after the pests have vacated. Keep in mind the blister beetle does not emit toxins until it is crushed or disturbed. Killing a beetle does not kill the poison but actually allows more to be emitted.

3. Do not use hay conditioners when reaping crops. This may reduce the number of beetles killed allowing them to move on when disturbed instead of spreading more toxin by being crushed. The danger to many animals is the crushed remains of the blister beetle and its poison being harvested up with hay bales.

4. Study insecticide options carefully before using. Read and follow all directions and keep in mind the blister beetle may move out on its own, leaving the residual effects of insecticide within harvested crops for no reason. Understand, also, the beetle may move in at any time and insecticides used early in the growing season may not be effective toward the end of the season.

5. Use insecticides wisely, checking fields for infestation before applying. If there is a great deal of infestation by blister beetles, use of heavy insecticide prior to harvest can be a great help. Beetles that are killed, initially, by insecticide should fall to the ground and be harder for machinery to pick up. Check areas carefully prior to harvesting and check all hay bales to be sure they are free of live or dead beetles before feeding to livestock.

References

• Cahri's Bugs Online; Blister Beetles; May 28, 2005
• Chemweb; Blister Beetle Intoxication
• Colorado State University; Blister Beetles in Forage Crops; K.K. Kinney, et al.: Aug. 20, 2010
• NDSU: Blister Beetles; Dean K. McBride; January 1992