Pheromone response inhibitors of the corn stalk borer Sesamia nonagrioides. Biological evaluation and toxicology

The behavioral activity of some trifluoromethyl ketones (TFMKs) as inhibito rs of the pheromone activity of the corn stalk borer Sesamia nonagrioides ( Lef.) (Lepidoptera: Noctuidae) is reported. The most closely-related analog ue to the pheromone tested. (Z)-11-hexadecenyl trifluoromethyl ketone (Z11- 16:TFMK), elicited a significant decrease in the number of male catches in traps baited with mixtures with the pheromone in 1:1 and 10:1 ratios in com parison to the pheromone alone. The E isomer of the analogue as well as two highly hydrated ketones, 3-octylthio-1,1,1-trifluoropropan-2-one (OTFP) an d 1,1-difluoropentadecyl trifluoromethyl ketone. were inactive. Conversely, the saturated TFMKs n-dodecyl trifluoromethyl ketone and, particularly, n- hexadecyl trifluoromethyl ketone induced a synergistic effect when mixed wi th the synthetic pheromone in 10: 1 ratio. However, in a wind tunnel these chemicals did not elicit any differential effect on flying moths attracted to a source containing a 10: 1 blend of the analogue and the pheromone. In a dual choice bioassay with two dispensers, containing the pheromone alone, and mixtures of Z11-16:TFMK and the pheromone and separated 5 cm apart, ma les showed no particular preference for either dispenser. The ketone mixtur e, however, induced moths to execute erratic flights with frequent crosswin d counter-turns and intersections with 1 lume boundaries. The total number of contacts with the source were reduced hen a control dispenser was paired with a dispenser containing Z11-16:TFMK and pheromone. Z11-16:TFMK and OTF P showed little toxicity on mice with a LD50 of 1 g/kg after the 6th day of treatment. For comparitive purposes, the major component of the pheromone, Z11-16:Ac, displayed a LD50 of 5 g/kg 6 days after application. Our result s provide additional information about the activity of the TFMKs, which mig ht be useful for the utilization of these chemicals in future pest control studies.