Development of a Survey Technique for Larvae of the Grass Webworm and Other Lepidopterous Species in Turfgrass 1

Abstract

Sampling techniques for larvae of the grass webworm, Herpetogramma licarsisalis (Walker) (Lepidoptera: Pyralidae) in turfgrass were studied. Sprinkling 1 liter of a 0.0015% aqueous solution of pyrethrins or 0.25% detergent into a 1,860-cm2 frame forced 61 and 55% of the larvae to the surface, respectively, compared with 4 liters of each irritant. The need for a greater volume of water than the commonly used technique of applying 4 liters/0.84 m2 was apparent. Continuous observation was required during the 10 min after application of either irritant to assure an accurate count, since 29% of the surfaced larvae reentered the thatch within 5 min and 38 to 39% reentered within 10 min. The detergent forced >50% of the larve to surface within 2 min. compared with 4 min with pyrethrins. Liquid irritants surfaced ca. 3 times more larvae in 5 to 10 min than plywood set out overnight. Similar responses to the presence of minor populations of the lawn armyworm, the black cutworm, and the fiery skipper indicate that other turf-infesting lepidopterous larvae may be sampled with the same techniques.