To manage black turfgrass ataenuis, what threshold triggers soil insecticide application?

• A. 30 per square inch
• B. 60 per square inch
• C. 120 per square inch
• D. 6 per square inch

Answer: (B)

Understanding when to treat hinges on the idea of an economic threshold: the pest density at which the cost of damage justifies the cost of control. For black turfgrass ataenuis, the turf is damaged primarily by the larvae feeding on roots, which reduces root mass and turf vigor. When the soil-dwelling population reaches a level that is likely to cause more economic loss than the cost of applying a soil insecticide, treatment is warranted.

The recommended threshold here is about 60 individuals per square inch. Reaching this density means there’s a high risk of significant root damage and ensuing turf decline, so applying a soil insecticide at that point helps protect the stand and prevent greater losses. In practice, you’d sample soil cores across the turf to estimate larval density, and if the average approaches this level, plan a treatment. Smaller infestations are often managed by monitoring and timing, since a low density may not justify the cost of treatment.