Monday, December 11, 2006

Lethal and sublethal effects of anion transport blockers against larvae of European corn borer, Ostrinia nubilalis (Hubner)

Dhana Raj Boina, and Jeffrey R. Bloomquist, Virginia Polytechnic Institute and State University, Department of Entomology, Blacksburg, VA

In this study, chloride ion transporter/exchanger blockers, 4,4-diisothiocyanato stilbene 2,2-disulfonic acid (DIDS), anthracene-9-carboxylic acid (9-AC), 5-nitro 2-(3-phenylpropyl amino) benzoic acid (NPPB), and indanyloxy acetic acid 94 (IAA-94), were tested against larvae of European corn borer, Ostrinia nubilalis (Hubner), for their lethal and sub-lethal effects using no-choice feeding bioassays. One late second instar larva/cup was allowed to feed on 6.25, 12.5, 25.0, or 50.0 ppm treated diet for 7 days followed by 14 days on untreated diet. The weight gain of larvae fed on DIDS (4.43-29.97 mg), NPPB (5.52-42.72 mg), 9-AC (14.68-42.17 mg), and IAA-94 (12.43-34.08 mg) at 12.5, 25, or 50 ppm for seven days was significantly less compared to control (48.49 mg) (P < 0.05). Larval mortality ranging from 20 (9-AC and IAA-94) to 40 % (NPPB) and 50 (9-AC) to 80% (NPPB) was observed at 25 and 50 ppm, respectively. Further, significant reduction in larval weight compared to control (P < 0.05) was recorded in treatments that were pretreated with 25 or 50 ppm and transferred to untreated diet for 14 days. Similarly, larval mortality in treatments that were pretreated with 25 ppm ranged from 20 (9-AC and IAA-94) to 45% (NPPB) and it was 70 (9-AC) to 100% (DIDS, NPPB, and IAA-94) in 50 ppm pretreated treatments. Consequently, number of days required for pupation in 25 or 50 ppm pretreated treatments significantly higher than in control (P < 0.05). The possible modes of action of these compounds underlying the observed toxicity were discussed.

Species 1: Lepidoptera Pyralidae Ostrinia nubilalis (European corn borer)