Intrapopulational changes in sex pheromone composition during scotophase in oriental tobacco budworm,Helicoverpa assulta (Guenée) (Lepidoptera: Noctuidae)

Abstract

Solvent extracts of individual pheromone glands were prepared from femaleHelicoverpa assulta (Guenée) at 2-hr intervals throughout the scotophase. The amounts of female sex pheromone components, (Z)-9-hexadecenal, (Z)-11-hexadecenal, (Z)-9-hexadecenyl acetate, and (Z)-11-hexadecenyl acetate, in the extracts were determined by gas chromatographic analysis. Although females called from early scotophase (2 hr) until late scotophase (6 hr) the quantity of extracted pheromone remained high at 8 hr, the end of the scotophase. More than 70% of the pheromone gland extracts contained sex pheromone components regardless of whether the donor females had been called or resting. Pheromone components were absent from gland extracts prepared at the onset of the scotophase. The quantity of (Z)-9-hexadecenal and (Z)-11-hexadecenal increased rapidly to reach a maximum of approximately 260 and 30 ng/female, respectively, that was maintained for up to 8 hr, the duration of the scotophase. The quantity of (Z)-9-hexadecenyl acetate and (Z)-11-hexadecenyl acetate increased continuously during the scotophase to peak at 600 and 30 ng/female, respectively, 8 hr into the scotophase. At the end of scotophase the quantity of all pheromone components decreased significantly.

Hybridization between Helicoverpa armigera and Helicoverpa assulta (Lepidoptera: Noctuidae): development and morphological characterization of F1 hybrids

“…Natural hybrids between these species have never been found in the field. Prezygotic isolation mechanisms probably play a potential role in preventing gene flow between two species (Wu et al, 1990;Park et al, 1996;Liu et al, 1994;Chen, 1999). The host-plant range of the two species is quite different.…”

Comparative study of sex pheromone composition and biosynthesis in Helicoverpa armigera, H. assulta and their hybrid

“…The variation could have been caused by collection of experimental insects from different areas. An approximately opposite ratio (7:100) of the two components was produced by females of H. assulta in China as their sex attractant pheromone (Liu et al, 1994) and this ratio was shown to vary with insect distribution and the pheromone release times in a light-dark cycle, but Z9-16:Ald was always a dominant component (Cork et al, 1992;Park et al, 1996). With species-specific ratios of the same sex pheromone components, these closely related species achieve reproduction isolation.…”

“…Relative amounts of Z11 and Z9-16:OAc found in the pheromone gland of H. assulta were even much higher than that of the corresponding aldehydes ( Table 2). The two acetates were identified as the sex pheromone components in a Korean population (Park et al, 1996), but not in the Chinese strain (Liu et al, 1994). In the pheromone gland of the hybrid, the ratio of Z9-16:Ald to Z11-16:Ald was determined as 4.0:100.…”

Insect semiochemical research in Korea: Overview and prospects

“…It was then found that an egg parasitoid Trichogramma chilonis was attracted to (Z)-11-hexadecenyl acetate (Z11-16:Ac), one of the sex pheromone components in a Korean population of H. assulta (Boo and Yang, 2000), leaving us the question whether the acetate plays the same role in Japan, China and Thailand because this compound is not present or is behaviorally inactive in H. assulta in these countries. In a Korean population, the ratios of the two acetate isomers, Z9-16:Ac and Z11-16:Ac, to the corresponding aldehyde isomers gradually changed in female H. assulta during the scotophase (Park et al, 1996). But, a small-scale field experiment showed that effective mating disruption for H. assulta could be achieved in a Korean hot pepper field with the Korean pheromone composition (Park et al, 1999).…”