R. E. Doolittle

Isolation and identification of allelochemicals that attract the larval parasitoid, Cotesia marginiventris (Cresson), to the microhabitat of one of its hosts

Volatiles released from corn seedlings on which beet armyworm larvae were feeding were attractive to females of the parasitoid,Cotesia marginiventris (Cresson), in flight tunnel bioassays. Analyses of the collected volatiles revealed the consistent presence of 11 compounds in significant amounts. They were: (Z)-3-hexenal, (E)-2-hexenal, (Z)-3-hexen-1-ol, (Z)- 3-hexen-1-yl acetate, linalool, (3E)-4,8-dimethyl-1,3,7-nonatriene, indole, α-trans-bergamotene, (E)-β-farnesene, (E)-nerolidol, and (3E,7E)-4,8,12-trimethyl-1, 3,7,ll-tridecatetraene. A synthetic blend of all 11 compounds was slightly less attractive to parasitoid females than an equivalent natural blend. However, preflight experience with the synthetic blend instead of experience with a regular plant-host complex significantly improved the response to the synthetic blend. Our results suggest thatC. marginiventris females, in their search for hosts, use a blend of airborne semiochemicals emitted by plants on which their hosts feed. The response to a particular odor blend dramatically increases after a parasitoid experiences it in association with contacting host by-products.

Identification of the Female Japanese Beetle Sex Pheromone: Inhibition of Male Response by an Enantiomer

(Z)-5-(1-Decenyl)dihydro-2(3H)-furanone, isolated from virgin female Japanese beetles (Popillia japonica) attracted males of the species infield bioassays. However, the synthesized racemic mixture of this compound did not attract male Japanese beetles. The Z and E isomers and the saturated analog of both enantiomers of this compound were synthesized stereospecifically. Pure synthetic (R,Z)-5-(1-decenyl)dihydro-2(3H)-furanone was competitive with live females and with the pheromone isolated from live females in attracting males. Male response was strongly inhibited by small amounts of the S,Z isomer. Although the E isomer and the saturated analog of the pheromone are present in the material obtained from females, the role of these compounds in mediating the insects behavior is unclear.

Isolation, identification, and synthesis of the sex pheromone of the tobacco budworm

The sex attractant of adult tobacco budworms,Heliothis virescens (F.) was isolated from ether washes of “calling” females and verified as active by field cage bioassays. The components of the pheromone were identified as (Z)-11-hexadecenal and (Z)-9-tetradecenal by spectroscopic and microdegradative methods. The two components are inactive when tested separately, but when they are mixed in the ratio in which they occur in female washes (16∶1, respectively), the synthesized mixture is equivalent to the natural one in attracting males in large cages. In field tests, 53 μg of synthesized mixture was competitive with four live females.

Isolation, identification, and synthesis of a female sex pheromone of the navel orangeworm,Amyelois transitella (Lepidoptera: Pyralidae)

A sex pheromone of the navel orangeworm,Amyelois transitella (Walker), was obtained from ether rinses of the sex pheromone gland of calling females. The pheromone was isolated by means of liquid and gas chromatography and was identified as one of four possible geometrical isomers of 11,13-hexadecadienal by means of spectroscopic and microchemical methods. Synthesis and laboratory bioassay of all four isomers revealed that only the (Z,Z) isomer was biologically active. (Z,Z)-11,13-hexadecadienal elicited quantitatively similar activation and attraction responses byA. transitella males as did the natural product.

Analysis, synthesis, formulation, and field testing of three major components of male mediterranean fruit fly pheromone

Three major components, ethyi-(E)-3-octenoate, geranyl acetate, and (E,E)-α-farnesene, emitted as volatiles by laboratory-reared and wild male medflies were collected and analyzed qualitatively and quantitatively. Peak emission of these compounds occurred during the third to fifth hours of the photophase and differences were observed in the ratios of the three components emitted by male laboratory-reared and wild flies. These three compounds were synthesized, and a method was developed to formulate a synthetic blend that released the compounds in a ratio similar to that emitted by wild male medflies. Attractiveness of the blend to female medflies was demonstrated under field conditions by comparing trap catches. Black spherical traps, baited with the synthetic blend to release 1.6 male equivalents, caught significantly more females than blank traps and traps from which the blend released was 0.3, 3.2 or 6.4 male equivalents.

Synthesis of the sex pheromone of the Japanese beetle.

The stereospecific synthesis of the sex pheromone produced by the female Japanese beetle (Popillia japonica Newman), (R,Z)-5-1-decenyl)-dihydro-2(3H)-furanone, is described. The pure syntheticR,Z form is a powerful attractant for males of the species in field bioassays and was competitive in attractiveness with live females, whereas the racemicZ isomer and theS,Z enantiomer were strong inhibitors of male response. The saturated analogs of both enantiomers were also synthesized stereospecifically.

Japanese beetle (Coleoptera: Scarabaeidae)

A combination of the synthetic sex attractant (R,Z)-5-(1-decenyl) dihydro-2(3H)-furanone with a 3∶7 mixture of phenethyl propionate (PEP) and eugenol (4-allyl-2-methoxphenol) caught significantly morePopillia japonica Newman than either the sex attractant or the mixture did alone. Also, the synthetic sex attractant captured significantly more males than the PEP-eugenol did during the period of heavy adult emergence of the beetles. The two lures were not significantly different in their attractancy to males about a week later and thereafter. A combination of PEP-eugenol and virgin females in the same trap late in the season also significantly increased beetle captures.

Biosynthesis of conjugated olefinic systems in the sex pheromone gland of female tobacco hornworm moths, Manduca sexta (L.)

Deuterium-labelled fatty acid putative precursors of the 16-carbon aldehydic sex pheromones of Manduca sexta (L.) were applied to the sex pheromone glands of females. After 24 h in vivo incubation, and injection of pheromone biosynthesis activating neuropeptide into the abdomens of treated females, glands were excised, extracted, and the extracts analyzed by gas chromatography-mass spectrometry. Incubation of glands with [16, 16, 16-2H3]hexadecanoic acid resulted in the label being incorporated into seven of the eight 16-carbon aldehydes found in the gland, including monoenes, dienes, and trienes. Similarly, incubation with [16, 16, 16-2H3](Z)-11-hexadecenoic acid led to incorporation of the label into (Z)-11-hexadecenal and both conjugated diene and triene aldehydes. However, incubation with [13, 13, 14, 14, 15, 15, 16, 16, 16-2H9](Z)-11-hexadecenoic acid resulted in incorporation of the label into only (Z)-11-hexadecenal, (E, Z)- and (E, E)-10, 12-hexadecadienal, indicating interference of the deuterium isotope in the desaturation process leading to the conjugated triene system. Incubation with the similarly labelled (E)-11-hexadecenoic acids gave labelled (E)-11-hexadecenal in both cases, but none of the other unsaturated pheromone aldehydes. The results indicate that fatty acids are the precursors of the aldehydic pheromones in this species and that hexadecanoate is the precursor of the 16-carbon monoenes, dienes, and trienes. The conjugated dienes and trienes are formed via desaturation/isomerization of (Z)-11-hexadecenoate.

Field tests of syntheticManduca sexta sex pheromone

In field experiments traps were baited with live females or with a two-, four-, or eight-component blend of the 16-carbon aldehydes previously identified as components of the sex pheromone emitted by femaleManduca sexta moths. The blends were formulated on rubber septa. Traps baited with a blend of all eight aldehydes captured moreM. sexta males than any other treatment. Septa loaded with 600 μg of the eight-component blend were attractive to males for about seven days in the field. Septa loaded with the eight-component blend and stored in a refrigerator at 4°C for a year released the conjugated diene and triene aldehydes at the same rate as freshly prepared septa and were equally attractive in the field.

Identification of the white peach scale sex pheromone

Micro techniques were used to obtain spectroscopic and degradative information from less than 5μg of the sex attractant of female white peach scale,Pseudaulascaspis pentagons (Targioni-Tozzetti) isolated from airborne collections. The pheromone was identified as (Z)-3,9-dimethyl-6-isopropenyl-3,9-decadien-1-ol propionate. Both enantiomers of theZ isomer and also the enantiomers of theE isomer were prepared from (R)-or (S)-limonene. Bioassays of material with minimum enantiomeric purity of 95% showed that at extreme dilution only theR,Z isomer attracted male white peach scale; however activity of theS,Z enantiomer could not be completely excluded.