6-Pentyl-2H-pyran-2-one: a potent peach-derived kairomone for New Zealand flower thrips, Thrips obscuratus.

New Zealand flower thrips, Thrips obscuratus (Thysanoptera: Thripidae), are attracted to ripening fruits, especially peaches. Volatiles from unripe and ripe peach fruits were collected and analyzed by gas chromatography/mass spectrometry. Six lactones were found only in ripe peach volatiles: γ-heptalactone, γ-octalactone, γ-nonalactone, 6-pentyl-2H-pyran-2-one, γ-decalactone, and δ-decalactone. When these compounds were tested individually in field-trapping experiments, three of them (γ-octalactone, γ-nonalactone, and 6-pentyl-2H-pyran-2-one) attracted New Zealand flower thrips. In another field-trapping experiment, aimed at testing various combinations of the three active compounds, no synergistic effects were found among all combinations tested; no combination caught more thrips than 6-pentyl-2H-pyran-2-one, alone. A further field-trapping experiment was conducted to determine the dose (10, 100, and 500 mg) of 6-pentyl-2H-pyran-2-one that gave the greatest catch of T. obscuratus, while also comparing it against another attractant, ethyl nicotinate, for T. obscuratus. The greatest catches in traps baited with either attractant were at loadings of 500 mg. At both 10 and 500 mg, traps baited with 6-pentyl-2H-pyran-2-one caught more T. obscuratus than those baited with the same amounts of ethyl nicotinate. 6-Pentyl-2H-pyran-2-one is a potent attractant for New Zealand flower thrips and, therefore, could be used for monitoring and control of New Zealand flower thrips. Work is underway developing monitoring and control options utilizing 6-pentyl-2H-pyran-2-one for this important pest.

Volatiles from apple trees infested with light brown apple moth larvae attract the parasitoid Dolichogenidia tasmanica.

The volatile compounds emitted from uninfested apple seedlings, cv. Royal Gala, and apple seedlings infested with generalist herbivore Epiphyas postvittana larvae were sampled using headspace collection and analyzed by gas chromatography-mass spectrometry. Nine additional compounds were only detected in infested apple seedlings [including benzyl alcohol, (E)-ß-ocimene, benzyl cyanide, indole, (E)-nerolidol, and four unidentified compounds]. Infested apple seedlings produced larger amounts of (Z)-3-hexenyl acetate, linalool, 4,8-dimethyl-1,3(E),7-nonatriene, methyl salicylate, ß-caryophyllene, germacrene D, (E,E)-α-farnesene, and (Z)-3-hexenyl benzoate than uninfested plants. Female parasitoids flew exclusively upwind to infested and not to uninfested apple seedlings in wind tunnel choice tests and preferred infested leaflets in still air, even after the removal of larvae. The attraction of a parasitoid to infested apple seedlings in the laboratory and in the field to apple and many other plants in at least six families supports considerable generality of the tritrophic signaling process.

Attraction of New Zealand flower thrips, Thrips obscuratus, to cis-jasmone, a volatile identified from Japanese honeysuckle flowers.

This work was undertaken to identify floral compound(s) produced by honeysuckle flowers, Lonicera japonica (Thunberg), that mediate the attraction of New Zealand flower thrips Thrips obscuratus (Crawford). Volatiles were collected during the day and night and analyzed by gas chromatography-mass spectrometry (GC-MS) to determine their emission over these two periods. Nine compounds were identified in the headspace; the main compound was linalool, and the other compounds were germacrene D, E,E-alpha-farnesene, nerolidol, cis-jasmone, cis-3-hexenyl acetate, hexyl acetate, cis-hexenyl tiglate, and indole. There was a quantitative difference between day and night volatiles, with cis-3-hexenyl acetate, hexyl acetate, cis-hexenyl tiglate, and cis-jasmone emitted in higher amounts during the day compared to the night. When the compounds were tested individually in field trapping experiments, only cis-jasmone attracted New Zealand flower thrips in a significant number. In another field trapping experiment, cis-jasmone caught similar numbers of New Zealand flower thrips compared to a floral blend formulated to mimic the ratios of the compounds emitted during the day, while catch with the night-emitted floral blend was not significantly different from the control. Subsequently, two field trapping experiments were conducted to determine the optimal attraction dose for cis-jasmone, a range of 1-100 mg loaded onto a red rubber stopper was tested, and the highest catches were in traps baited with 100 mg loading. A higher range of 100-1000 mg loaded into polyethylene vials was tested, and the highest catch was in traps baited with 500 mg. In another experiment aimed at comparing the attraction efficacy of cis-jasmone with the two other known thrips attractants (ethyl nicotinate and p-anisaldehyde), ethyl nicotinate showed the highest trap catch followed by cis-jasmone. A smaller number of Thrips tabaci (Lindeman) was attracted to traps baited with cis-jasmone. These results suggest that cis-jasmone might act as a kairomone that mediates the attraction of New Zealand flower thrips to the flowers of the Japanese honeysuckle.

Floral scent of Canada thistle and its potential as a generic insect attractant.

The flowers of Canada thistle, Cirsium arvense (L.), attract a wide range of insects, including pollinators and herbivorous species. This attraction is primarily mediated by floral odor, which offers potential for developing generic insect attractants based on odor. In this study, we have analyzed the chemical composition of the volatiles produced by Canada thistle flowers. Nineteen floral compounds were identified in the headspace, including phenylacetaldehyde (55%), methyl salicylate (14%), dimethyl salicylate (8%), pyranoid linalool oxide (4.5%), and benzaldehyde (3.5%). Other minor compounds include benzyl alcohol, methylbenzoate, linalool, phenylethyl alcohol, furanoid linalool oxide, p-anisaldehyde, 2,6-dimethyl-1,3,5,7-octatetraene, benzylacetate, benzyl tiglate, (E,E)-alpha-farnesene, benzyl benzoate, isopropyl myristate, and 2-phenylethyl ester benzoic acid. The relative attractiveness of various doses of the main floral volatile compound phenylacetaldehyde (i.e., 10, 100, 200, and 400 mg) was tested for insect attraction. Both the total catch and the biodiversity of insect species trapped increased as the loading of phenylacetaldehyde increased. Volatiles were chosen from the odors from the flowers of Canada thistle and formulated and tested in the field. An 11-component blend was the most attractive of several floral blends tested. These findings indicate that chemical components of flower odors of Canada thistle can serve as a generic insect attractant for monitoring of invasive pest species.

Regulation of Photosynthetic Rate of Two Sunflower Hybrids under Water Stress.

The effect of short-term water stress on photosynthesis of two sunflower hybrids (Helianthus annuus L. cv Sungro-380 and cv SH-3622), differing in productivity under field conditions, was measured. The rate of CO(2) assimilation of young, mature leaves of SH-3622 under well-watered conditions was approximately 30% greater than that of Sungro-380 in bright light and elevated CO(2); the carboxylation efficiency was also larger. Growth at large photon flux increased assimilation rates of both hybrids. The changes in leaf composition, including cell numbers and sizes, chlorophyll content, and amounts of total soluble and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) protein, and in Rubisco activity and amount of ribulose-1,5-bisphosphate (RuBP) were determined to assess the factors regulating the differences in assimilation of the hybrids at high and low water potentials. The amounts of chlorophyll, soluble protein, Rubisco protein and the initial activity of Rubisco and its activation state did not differ significantly between hybrids. However, unstressed leaves of SH-3622 had more, smaller cells per unit area and 60% more RuBP per unit leaf area than that of Sungro-380. Water stress developing over 4 days decreased the assimilation of both hybrids similarly. Changes in the amounts of chlorophyll, soluble and Rubisco protein, and Rubisco activity and activation state were small and were not sufficient to explain the decrease in photosynthesis; neither was decreased stomatal conductance (or stomatal "patchiness"). Reduction of photosynthesis per unit leaf area from 25 to 5 micromoles CO(2) per square meter per second in both hybrids was caused by a decrease in the amount of RuBP from approximately 130 to 40 micromoles per square meter in SH-3622 and from 80 to 40 micromoles per square meter in Sungro. Differences between hybrids and their response to water stress is discussed in relation to control of RuBP regeneration.