Showing papers by "Jocelyn G. Millar published in 1994"

Interaction of the Culex quinquefasciatus egg raft pheromone with a natural chemical associated with oviposition sites.

Abstract: In laboratory bioassays, gravid Culex quinquefasciatus mosquitoes were strongly attracted and or stimulated to oviposit by a habitat-derived chemical cue, 3-methylindole, at several concentrations ranging from 0.01 to 1 microgram/liter in water. At concentrations above 10 micrograms/liter, 3-methylindole became repellent or deterrent. Responses to the known egg raft pheromone, 6-acetoxy-5-hexadecanolide, were much weaker and were relatively constant above a threshold dosage of about 0.1 microgram. Responses to blends of a fixed amount of the pheromone with variable doses of 3-methylindole were shown to be additive rather than synergistic.

Topical Toxicity of Tomato Sesquiterpenes to the Beet Armyworm and the Role of These Compounds in Resistance Derived from an Accession of Lycopersicon hirsutum f. typicum

Abstract: The topical toxicity of five sesquiterpenes to neonate beet armyworm (Spodoptera exigua [Hubner]) was determined to be sufficiently high (LD 50 from 3 to 10 μg/larva) to implicate these compounds as resistance factors in sesquiterpene-producing accessions of Lycopersicon hirsutum f. typicum Humb. and Bonpl. (hir). Three sesquiterpenes (zingiberene and two anomers of elemene) were present at 33 μg/cm 2 on intact leaf surfaces of a genotype of hair accession PI 126445. Ten-day survival of S. exigua larvae on foliage of than genotype was 0%, but removal of 90% of the sesquiterpenes by wiping the foliage with methanol increased S. exigua survival to 65%

Field evaluation of synthetic compounds mediating oviposition inCulex mosquitoes (Diptera: Culicidae).

Abstract: 3-Methylindole (skatole), a compound shown to be an oviposition attractant/stimulant forCulex quinquefasciatus in laboratory tests, was evaluated against natural populations of mosquitoes in the field. In experiments using paired black plastic tubs that contained water treated with an attractant solution containing a mixture of 3-methylindole, 4-methylphenol, 4-ethylphenol, phenol, and indole or that contained only tap water, the attractantbaited traps received significantly moreCx. quinquefasciatus egg rafts than did the untreated tap water. Gravid female traps that were baited with attractant solution collected significantly moreCx. quinquefasciatus females than did traps containing only tap water. There was no significant difference in number ofCx. quinquefasciatus collected in the traps baited with the attractant solution compared to the traps that contained water with 3-methylindole alone, indicating that 3-methylindole was solely responsible for the attraction. In replicated experiments conducted in experimental ponds, ponds that were treated with 3-methylindole received significantly moreCx. quinquefasciatus, Cx. tarsalis, andCx. stigmatosoma egg rafts than did untreated ponds. Experimental ponds treated with 3-methylindole at two levels (0.12 and 0.6 mg/liter) were equally attractive to ovipositingCx. quinquefasciatus. This is the first record of 3-methylindole showing attractancy/stimulation to ovipositingCx. stigmatosoma andCx. tarsalis under field or laboratory conditions.

Effects of host plant,Gossypium hirsutum L., on sexual attraction of cabbage looper moths,Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae)

Abstract: Unmated female or male cabbage looper moths,Trichoplusia ni (Hubner), were attracted more often in a flight tunnel to a cage with moths of the opposite sex and a bouquet of cotton foliage. Increased sexual attractiveness of females with plants may be a result of stimulation of pheromone release in response to plant odor, since more males were attracted when odor of cotton foliage was passed over females than when odor of females was passed over cotton foliage before venting into the flight tunnel. Increased sexual attractiveness of males with plants is due in part to host odor enhancement of female attraction to male pheromone, since more females were attracted to synthetic male pheromone (a blend of enantiomers of linalool and isomers of cresol) and a cotton leaf extract than were attracted to male pheromone alone. A short synthesis procedure was developed for (S)-(+)-linalool, the major component of the male sex pheromone, isolated from hair pencils, used in these tests.

Protein hydrolysates and associated bacterial contaminants as oviposition attractants for the mosquito Culex quinquefasciatus

Abstract: Six protein or protein hydrolysate solutions were tested for activity as attractants for ovipositing Culex quinquefasciatus mosquitoes in the laboratory. Four of these solutions (egg albumin, lactalbumin hydrolysate, casein hydrolysate and yeast hydrolysate) were attractive to ovipositing females at varying concentrations, when compared to distilled water controls. Soy hydrolysate was repellent at 1%, but not significantly attractive or repellent at lower concentrations. 'Nulure', a tephritid fly bait containing protein hydrolysate, also had no significant effect on oviposition behaviour. Gravid females mostly oviposited within the first 4 h of the scotophase, regardless of the presence or absence of an oviposition attractant. Lactalbumin hydrolysate 1% solution, with or without 0.1% neomycin antibiotic, was attractive to Cx quinquefasciatus. This effect was reduced by the presence of neomycin which, alone, had no effect on oviposition. Hence both lactalbumin hydrolysate and bacterial contaminants were shown to be attractive to gravid Cx quinquefasciatus.

Identification of volatile compounds from fungus‐infected date fruit that stimulate upwind flight in female Ectomyelois ceratoniae

Abstract: Four volatile compounds emitted from fungus-infected date fruit, Phoenix dactylifera L., were identified using coupled gas chromatographic-electroantennographic recordings, coupled gas chromatographic-mass spectrometric analysis, electroantennographic assays of synthetic standards, and wind tunnel bioassays These compounds were ethyl hexanoate, ethanol, acetaldehyde, and 2-phenylethanol Wind tunnel bioassays showed that ethyl hexanoate was capable of stimulating upwind flight and landing on the souice by mated female carob moths, Ectomyelois ceratoniae (Zeller) Addition of both ethanol and acetaldehyde to ethyl hexanoate resulted in an increase in attraction to a level similar to that found for date fruits No such effect was noted for additions of 2-phenylethanol at the dosages tested In this study, it appears that ethyl hexanoate is a dominant olfactory stimulant and attractant for mated female carob moths, and represents a novel compound with regard to previously identified lepidopteran host odor attractants,

Phthalide-based host-plant resistance toSpodoptera exigua andTrichoplusia ni inApium graveolens.

Abstract: A chemical basis for the difference in suitability between two celeriac (Apium graveolens var.rapaceum) cultivars for the survival and growth ofSpodoptera exigua (Hubner) andTrichoplusia ni (Hubner) was identified as sedanenolide (3-n-butyl-4,5-dihydro-isobenzofuranone). Sedanenolide was isolated using a bioassay-driven extraction and purification procedure and was identified using several spectrometric methods. Foliar concentrations of sedanenolide were negatively correlated with larval performance and were significantly higher in the cultivar less suitable for larval survival and growth. Sedanenolide andBacillus thuringiensis Berliner acted additively in reducing larval growth when combined in artificial diets, a result that is consistent with previous studies in which the combined effect of host plant cultivar andB. thuringiensis on larval survival and growth were additive.