BLISTER BEETLE MANAGEMENT

The transition into second and third alfalfa cuttings in Oklahoma is the time to think about blister beetles and minimizing their risk. First, some facts about blister beetles:   

• The species of blister beetles found in Oklahoma are distributed throughout the United States. The problem is not restricted to this area. Don't believe the stories that only certain states have blister beetles in hay.  
• Many people try to pin down the number of blister beetles it takes to kill a horse. As you may guess, it varies with size, age and other factors, but most of the research in this area suggests that it takes 15 to 30 beetles to cause horses to be ill and considerably more to cause mortality.  
• Is there a relationship between blister beetles and grasshoppers? Yes, a relationship exists -- but a delayed one. Blister beetle larvae feed on grasshopper egg pods in the soil. When there are high numbers of grasshoppers one year, probably there will be high numbers of blister beetles the next year.  

• Match cuttings and markets. Early-May and late-September harvests are before and after the major blister beetle season. Target these cuttings for horse buyers.  
• Utilize an insecticide before harvest, but make sure the product has no waiting period before harvest. Malathion has a 0-day waiting period, and Sevin^® has a 7-day waiting period. Target the market before spraying to be sure the premium from the buyer justifies application costs.  
• Do not use a crimper when swathing alfalfa hay. Crimpers crush beetles into the hay and kill them. A simple cutter bar cuts very few insects and they fall to the ground. The live ones fly away as the hay wilts.  
• Watch carefully when swathing. However, even large swarms can be overlooked by experienced operators.  
• Try to eliminate or minimize tire traffic on cut or uncut hay. This will reduce crushing beetles into the hay swath. Remember, a dead beetle is just as toxic to a horse as a live one.