Apparatus and procedure for measuring release rates from formulations of lepidopteran semiochemicals

An apparatus was developed wherein a vacuum source was used to pull air across a controlled-release-formulation dispenser or a planchet containing a known quantity of a semiochemical and into a collector filled with a polymeric adsorbent. After a set time, the semiochemical was eluted with solvent and was quantified by gas-liquid chromatography (GLC). High percentages of known quantities of the lepidopteran semiochemicals (Z)-7-dodecen-l -ol acetate (Z7DDA), boiling point (bp) 275 ° C/1 atm, (Z)-9-tetradecen-1-ol formate (Z9TDF), bp 289 °C/1 atm, and (Z,Z)-3,13-octadecadien-1-ol acetate (ZZODDA), bp 490 °C/1 atm, were recovered. The semiochemicals did not oxidize and were recovered quantitatively from the adsorbent. The release rates of Z9TDF from a controlled-release dispenser were found to be directly proportional to the airflow rates. Release rate measurements on the Z9TDF dispensers were made for the purpose of estimating the method's precision. The method was shown to give internally consistent results by measurements on another Z9TDF formulation. The accuracy of the method is discussed.Mention of a commercial or proprietary product in this paper does not constitute an endorsement by the USDA.     

Properties of cuticular oxidases used for sex pheromone biosynthesis byHeliothis zea

Biosynthesis of the aldehydic sex pheromone components released by females ofHeliothis zea was found to be catalyzed by primary alcohol oxidases residing in the cuticle that covers the glands. Activity, as indicated by conversion of primary alcohol to aldehyde, was as high in cell-free cuticle as it was in intact pheromone glands. Studies indicated that some activity was associated with the surface of the epicuticle and could be removed, into buffer, by sonication. However, the majority of activity lies within the inner epicuticle and exo- and endocuticular layers. The oxidase was not functional in pharate pupae that did not have mature adult cuticle but became functional just prior to adult emergence. The enzyme in individual glands was saturated at alcohol concentrations above 100 n. moles. Nonionic detergents did not affect the activity of the oxidase in the cuticle but treatment with either 7 M urea or 1% SDS resulted in total loss of activity. Studies on the effect of pH indicated an optimum at 6.4; however, activity was high throughout the range of 5–9. The oxidase was functional in both dichloromethane and hexane, suggesting that this enzyme system may have applications for organic synthesis of aldehydes.     

Specificity of Systemically Released Cotton Volatiles as Attractants for Specialist and Generalist Parasitic Wasps

Cotton plants under herbivore attack release volatile semiochemicals that attract natural enemies of the herbivores to the damaged plant. The volatiles released in response to herbivory are not only released from the damaged leaves but from the entire cotton plant. We found that cotton plants that released myrcene, (Z)-3-hexenyl acetate, (E)--ocimene, linalool, (E)-4,8-dimethyl-1,3,7-nonatriene, (E)--farnesene, and (E, E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene systemically from undamaged leaves of caterpillar damaged plants were attractive to the generalist parasitoid Cotesia marginiventris and the specialist parasitoid Microplitis croceipes. Plants from which the caterpillar damaged leaves were removed and that released those compounds systemically were significantly preferred over undamaged control plants in two-choice experiments in a flight tunnel. Artificially damaged cotton plants that released green leafy volatiles and constitutive terpenoids were less attractive for M. croceipes and C. marginiventris. Only C. marginiventris preferred artificially damaged plants over undamaged control plants, whereas M. croceipes showed no preference. The apparent lack of specificity of systemically released compounds in response to different herbivores feeding on the lower leaves is discussed.     

Identification and Synthesis of Volicitin and Related Components from Beet Armyworm Oral Secretions

Oral secretion of beet armyworm caterpillars (BAW), when applied to damaged tissues of corn seedlings, induces the seedlings to emit volatile compounds that attract the natural enemies of the caterpillars. The key elicitor present in BAW oral secretions is N-[17-hydroxylinolenoyl]-L-glutamine (volicitin). Analysis of the oral secretion showed that it also contained N-[17-hydroxyolinoleoyl]-L-glutamine, free 17-hydroxylinolenic, and 17-hydroxylinoleic acid, the glutamine conjugates of linolenic and linoleic acid as well as free linolenic and linoleic acid. Here we present the identification and synthesis of the hydroxy acids and of glutamine conjugates.     

Response to pheromone traps and disruption of pheromone communication in the lesser peachtree borer and the peachtree borer (Lepidoptera: Sesiidae)

The sex pheromone communication of the lesser peachtree borer,Synanthedon pictipes (Grote and Robinson), and the peachtree borer,Sanninoidea exitiosa (Say), can be disrupted by permeation of the atmosphere with their respective sex pheromones, (E,Z)- and (Z,Z)-3,13-octadecadien-1-ol acetate. The two isomers seemed equally effective against both species. Disruption was greatest when the pheromone was evaporated from the tops of the peach trees; also, pheromone traps placed in the tree tops captured significantly more males than did traps placed lower in the trees. Neither the color nor the directional placement in a tree (NE, NW, SE, SW) of pheromone-baited traps influenced captures of male lesser peachtree borers.Mention of a commercial or proprietary product in this paper does not constitute a recommendation or an endorsement of that product by the USDA.     

Miniature endoscope for simultaneous optical coherence tomography and laser-induced fluorescence measurement

We have designed a multimodality system that combines optical coherence tomography (OCT) and laser-induced fluorescence (LIF) in a 2.0-mm-diameter endoscopic package. OCT provides approximately 18-microm resolution cross-sectional structural information over a 6-mm field. LIF spectra are collected sequentially at submillimeter resolution across the same field and provide histochemical information about the tissue. We present the use of a rod prism to reduce the asymmetry in the OCT beam caused by a cylindrical window. The endoscope has been applied to investigate mouse colon cancer in vivo.     

Volatiles from Intact and Lygus-Damaged Erigeron annuus (L.) Pers. are Highly Attractive to Ovipositing Lygus and its Parasitoid Peristenus relictus Ruthe

Trap cropping and biological control can provide a sustainable means of controlling insect pests. Insects in the genus Lygus (Hemiptera: Miridae) are major pests on cotton and horticultural crops throughout the United States, and pesticide resistance within Lygus populations necessitates more sustainable long-term management techniques. Here, we explore behavioral responses of Lygus bugs (L. rubrosignatus Knight) and an introduced parasitoid, Peristenus relictus (Hymenoptera: Braconidae), to a common field edge plant, Erigeron annuus, which has the potential to serve as a trap host. Erigeron annuus is attractive to Lygus in the field, with Lygus preferentially moving to Erigeron patches compared to more abundant cotton plants. To determine the role of odor cues in mediating this attraction, we collected volatiles from E. annuus with and without Lygus damage, and then tested the attractiveness of these volatiles vs. those of cotton to Lygus females and female P. relictus wasps using Y-tube and wind tunnel bioassays. We found that undamaged E. annuus emits high concentrations of a complex volatile blend (60+ compounds), with novel compounds induced and constitutive compounds up-regulated in response to damage. Additionally, both female Lygus bugs and female P. relictus wasps are highly attracted to E. annuus volatiles over those of cotton in almost every combination of damage treatments. Our results suggest that Erigeron annuus would be an effective trap plant to control Lygus in cotton, since it is highly attractive to both the pest and its natural enemy.     

Prediction of release ratios of multicomponent pheromones from rubber septa

A method has been developed to predict the release ratio of the components of blends of alcohols, acetates, and/or aldehydes from rubber septa. The calculations of predicted release ratios are based on the relative vapor pressures of the components. The relative vapor pressures of the compounds were calculated from their retention indices on a liquid crystal capillary gas chromatographie column. The correlation between the theoretically predicted and experimentally determined ratios was very good. Thus, formulations can be prepared that will release a desired ratio of the components of a multicomponent pheromone blend.Mention of a commercial or proprietary product does not constitute an endorsement by the USDA.     

Isolation,identification, and synthesis of male-produced sex pheromone of papaya fruit fly,Toxotrypana curvicauda Gerstaecker (Diptera: Tephritidae)

A male-produced sex pheromone of the papaya fruit fly,Toxotrypana curvicauda Gerstaecker, was isolated from volatiles collected from air passed over calling males and was identified as 2-methyl-6-vinylpyrazine by comparative gas-liquid chromatographic and spectroscopic evidence. Synthetic 2-methyl-6-vinylpyrazine elicited typical pheromonal responses from unmated mature female flies such as walking, running, and flying in an arena bioassay; flying upwind with a zigzag flight pattern; and hovering in the pheromone plume in a wind-tunnel bioassay. These responses were similar quantitatively and qualitatively to responses to naturally occurring pheromone from calling male papaya fruit flies.This article reports the results of research only. Mention of a proprietary product does not constitute an endorsement or the recommendation for its use by USDA.