Cumulative trap catches are shown for participating counties. When 200 pale western cutworm moths or 800 army cutworm moths or more have been trapped the potential for a damaging larval population of these species is great. However, these thresholds are highly influenced by environmental conditions that occur between moth flight and damage by larvae. Larval Monitoring Larvae of either species generally are not active above ground on bright, sunny days. They can be found just below ground by scraping the soil surface lightly.
Small larvae are well-camouflaged and can be difficult to see in the soil.
Larval densities can be assessed by digging and screening the soil from one foot of row or a square foot at different sites in the field. Soil samples should be dug to a depth of at least 3 inches. However, soil sieving is both labor and time intensive and has limited practicality as a routine sampling method. Examining plants for signs of cutworm larval activity and for cumulative larval damage is a more practical approach to assessing larval populations. Damage by cutworms can be distinguished from winter kill by looking carefully for evidence of feeding damage.