FUMIGANT PROPERTIES OF PHYSICAL PREPARATIONS FROM MOUNTAIN BIG SAGEBRUSH, ARTEMISIA-TRIDENTATA NUTT. SSP. VASEYANA (RYDB.) BEETLE FOR STORED GRAIN INSECTS

Vapors released from foliage of mountain big sagebrush, Artemisia trid entata Nutt. ssp. vaseyana (Rydb.) Beetle, through a patented process, were hypothesized to have an insecticidal time of action (24 h or les s after time of exposure) similar to the fumigant methyl bromide. Pate nted preparations were more effective from plants harvested from a rel atively wet site in mid to late summer (5 July to 11 September). Bioas says with the lesser grain borer, Rhyzophertha dominica (F.), 0-3 days after adult emergence indicated an LT50 of 7.0 +/- 1.2 h for the vola tiles generated from only 30 mg dry processed plant material (= 0.56 m g active ingredients) per mi headspace. Hatching of eggs of the Indian meal moth, Plodia interpunctella (Hubner), was completely suppressed when exposed 4-20 h after oviposition to a concentration of 7 mg proce ssed plant material per mi headspace (= 0.14 mg active ingredients) in a container that allowed passive diffusion and from which the terpene s disappeared by 48 h. Adult red flour beetle, Tribolium castaneum (He rbst), had an LT50 of 40.7 +/- 1.2 h when exposed to 29 mg processed p lant material per mi headspace. Gas chromatography/mass spectrometry ( GC/MS) analyses of the headspace above this processed plant material r evealed five major peaks, all non-chlorinated and non-brominated. The two main volatiles, 1,8-cineole and camphor, occurred initially in a m ean ratio of 1:3.2, gradually shifting to 1:2.4 over 24 h. The mu g/ m i headspace of each detectable compound in a sealed container was foll owed intensely (0.25, 1, 2, 12, 24, 48, and 72 h) for 72 h and at less frequent intervals for 60 days. The active compounds released by the plant material in a closed, but not airtight container, were no longer detectable after 2 1 h based on GC/MS analysis. Fumigative studies wi th the same ratio of the two main compounds generated synthetically in dicated that embryos of P. interpunctella and adults of R. dominica we re as sensitive to the synthetic mixture as they were to the processed plant material; Although one could apply the precise commercial terpe nes in the same ratio, the plant material provides a natural formulati on that is conveniently diluted (formulated) to levels safe for handli ng. Therefore, this preparation method and plant material shows good p otential as an alternative to methyl bromide for protection of stored grain, commodity, and space fumigations. No residues are detectable in the headspace of aerated commodity, milled product, or in fumigated s pace. (C) 1998 Elsevier Science Ltd. All rights reserved.