Chemically-mediated colonization of black cherry by the peach bark beetle, Phloeotribus liminaris.

The peach bark beetle (Phloeotribus liminaris Harris, PBB) affects the health, quality, and value of black cherry (Prunus serotina Ehrh.) within the Central Hardwoods Forest Region of North America. When colonized by adult beetles, black cherry trees produce a defensive exudate, or 'gum', staining the wood and decreasing its value up to 90%. Current management tactics are inadequate to avoid extensive damage to most veneer-sized black cherry in the region. We test the hypothesis that PBB colonization behavior is chemically-mediated and determine the extent to which PBB is attracted to compounds associated with wounded or PBB-infested cherry wood. Through olfactometer and field bioassays, we determined that adult PBB were attracted to cherry branches infested with female beetles. We then used dynamic headspace sampling to collect volatiles associated with wounded and infested bolts of black cherry. The volatile benzaldehyde dominated these collections and was more abundant in aerations of female-infested bolts than other odor sources. In subsequent field bioassays, we evaluated the bioactivity of benzaldehyde, as well as α-longipinene, in combination with several chemical carriers. Traps baited with benzaldehyde captured more PBB than all other treatments, irrespective of other lure components. Moreover, PBB were not attracted to traps baited solely with ethanol, a common attractant for bark beetles that colonize hardwood trees. This is the first report of benzaldehyde as an attractant for a species of bark beetle and could aid in developing semiochemical-based management tactics for this important pest.

Do Helicoverpa armigera Moths Signal Their Fecundity by Emission of an Antagonist?

Female Helicoverpa armigera emit a pheromone, comprised of a 98:2 ratio of (Z)-11-hexadecenal to (Z)-9-hexadecenal, to attract males. It has been proposed that "immature" female H. armigera modulate attraction of males by emitting an antagonist, (Z)-11-hexadecenol, along with pheromone during the first two nights of calling. However, it is unclear why females would call and simultaneously release pheromone and an antagonist. We conducted observations of female calling during the first five nights after adult emergence to determine periodicity. We also measured the relative abundance of (Z)-11-hexadecenol to the major component, (Z)-11-hexadecenal, on the surface of the gland of calling females and compared it to the ratio of these two compounds inside the gland over the first three nights after adult emergence to determine how much antagonist may be released. We found that young females (< 1-d-old) are unlikely to call and, based on the relative proportion of (Z)-11-hexadecenol on the gland surface, even if they did call would be unlikely to release sufficient (Z)-11-hexadecenol to diminish male attraction.

Volatile and Contact Chemical Cues Associated with Host and Mate Recognition Behavior of Sphenophorus venatus and Sphenophorus parvulus (Coleoptera: Dryophthoridae).

Beetles in the genus Sphenophorus Schönherr, or billbugs, potentially utilize both volatile and non-volatile behavior-modifying chemical signals. These insects are widely distributed across North America, often occurring in multi-species assemblages in grasses. However, details about their host- and mate-finding behavior are poorly understood. This study tested the hypothesis that volatile organic compounds from host-plants and conspecifics direct the dispersal behavior of hunting billbug S. venatus Say. Further, we characterized the cuticular hydrocarbon profiles of two widespread pest species, S. venatus and bluegrass billbug S. parvulus Gyllenhaal, to assess the potential role of contact pheromones in mate-recognition. In Y-tube olfactometer bioassays, S. venatus males were attracted to a combination of conspecifics and Cynodon dactylon host-plant material, as well as C. dactylon plant material alone. S. venatus females were attracted to a combination of male conspecifics and host-plants but were also attracted to male conspecifics alone. Field evaluation of a putative male-produced aggregation pheromone, 2-methyl-4-octanol, identified from two congeners, S. levis Vaurie and S. incurrens Gyllenhaal, did not support the hypothesis that S. venatus and S. parvulus were also attracted to this compound. Gas chromatography-mass spectrometry analysis of S. venatus and S. parvulus whole-body cuticular extracts indicated a series of hydrocarbons with qualitative and quantitative interspecific variation in addition to intraspecific quantitative variation between males and females. This study provides the first evidence that S. venatus orients toward host- and insect-derived volatile organic compounds and substantiates the presence of species-specific cuticular hydrocarbons that could serve as contact pheromones for sympatric Sphenophorus species.

Toxicity of Turmeric Extracts to the Termite Reticulitermes flavipes (Blattodea: Rhinotermitidae).

Turmeric is an important spice crop with documented human health benefits associated with chemicals called curcuminoids. In this study, the termite Reticulitermes flavipes (Kollar) was exposed to different solvent extracts of turmeric to investigate potential termiticidal properties. Treating termites with hexane extracts of purified lab-grade curcuminoids had no effect on termites. However, in continuous exposure assays, the LC(50) for hexane extracts of crude turmeric powder was 9.6 mg, or 1.0 mg starting material per square centimeter of filter paper substrate. These active components were soluble in a range of polar and apolar solvents, but only hexane could selectively fractionate active components away from the inactive curcuminoids. The active constituents of turmeric separated by thin layer chromatography (TLC) fluoresced in short-wave UV light but were not visible in long-wave UV light. By re-extracting TLC-separated bands in hexane and performing bioassays and gas chromatography-mass spectrometry, we demonstrated that termiticidal components of turmeric are extractable as a blend containing mainly ar-turmerone, turmerone, and curlone. This determination is consistent with findings of preceding work by other researchers that investigated insecticidal properties of turmeric in other pest insects.

Determination of the Absolute Configuration of Female-Produced Contact Sex Pheromone Components of the Longhorned Beetle, Neoclytus acuminatus acuminatus (F).

Cuticular hydrocarbons play important roles in contact chemical communication in insects. Many of these compounds are methyl-branched hydrocarbons with one or more chiral centers, which can exist in two or more stereoisomeric forms. Although the importance of chirality for the volatile semiochemicals that insects use for long-range communication is well established, almost nothing is known about the role of chirality in insect contact chemoreception. Here, we used reverse phase high performance liquid chromatography (RP-HPLC) and digital polarimetry to isolate and determine the absolute configuration of a component of the female-produced contact sex pheromone of the cerambycid beetle, Neoclytus acuminatus acuminatus (F.). The pheromone consists of 7-methylpentacosane (7-MeC25), 7-methylheptacosane (7-MeC27), and 9-methylheptacosane (9-MeC27). The absolute configuration of the most abundant pheromone component, 7-MeC25, was found to be (R). We then utilized enantiomerically pure synthetic pheromone components to test the hypothesis that males would respond more strongly to (R)- than to (S)-enantiomers of the three pheromone components. We also tested blends of (R)-7-MeC27, the most bioactive component, with the (S)-enantiomers of the minor components and vice versa to determine if unnatural stereoisomers might decrease behavioral responses. Males responded most strongly to solvent-washed females treated with the blend of (R)-pheromone components, and to a lesser extent to (R)-7-MeC27 alone. A blend of (R)-7-MeC27 with the (S)-minor components elicited an intermediate response. Together, these findings suggest that the insects can discriminate the absolute configuration of the major and minor pheromone components, and that the configuration of all three components is likely to be (R).