Field Trials and Laboratory Bioassays of CME 134, a New Insect Growth Regulator, Against Heliothis zea and Other Lepidopterous Pests of Soybeans

Abstract

We conducted field experiments in 1982 and 1983 in central Alabama to determine the effectiveness of CME 134, a new insect growth regulator with molt-inhibiting activity, on immature lepidopterous pests of soybeans including the soybean looper ( Pseudoplusia includens [Walker]), the corn earworm ( Heliothis zea [Boddie]), the green cloverworm ( Plathypena scabra [Fabr.]), and the velvetbean caterpillar ( Anticarsia gemmatalis Hubner). CME 134 was applied in doses of 16.5, 33.0, 66.0, 132.0, and 264.0 g (AI)/ha. CME 134-treated plots remained almost completely free of lepidopterous pests for at least 55 days after application in the 1982 tests, demonstrating high residual activity. Results of laboratory experiments suggested that residual activity was maintained through larvicidal activity of CME 134 residues on leaf surfaces. Dosage-mortality responses were determined for CME 134 against Heliothis zea larvae by continuous feeding on diet media in which the product was incorporated. LC50 values following 7 days of exposure were 21.9, 18.2, and 24.0 μg (AI)/ml diet medium for first-, third-, and fourth-instar larvae, respectively. LC50 values based on total larval + pupal mortality in insects initially exposed in the same three instars were 2.8, 2.2, and 3.7μg(AI)/ml medium, respectively. Dosage-mortality regressions for total larval + pupal mortality did not differ among instars. Early instars in general, died more rapidly than did later instars. Later instars died during the prepupal-to-pupal transformation.