Geographical variation in female sex pheromones of the rice leaffolder moth, Cnaphalocrocis medinalis: identification of pheromone components in Japan

Abstract

Sex pheromone components of the Japanese rice leaffolder moth, Cnaphalocrocis medinalis Guenée (Lepidoptera: Pyralidae) were identified from ovipositor extracts of virgin females as (Z)‐11‐octadecenal, (Z)‐13‐octadecenal, (Z)‐11‐octadecen‐1‐ol and (Z)‐13‐octadecen‐1‐ol at a ratio of 11:100:24:36 by GC‐EAD, GC, GC‐MS. The total amount was estimated to be ca.0.9 ng/female. Field bioassays in Kagoshima, Japan, showed that the two aldehydes are essential for male attraction and the alcohols may have a synergistic effect on the aldehydes. A rubber septum containing 0.9 mg of the four components at the natural ratio was shown to be an effective lure for monitoring this pest in Japan. The above four components are quite different from the sex pheromone components reported previously for the same species of either Philippine or Indian origin; components were shown to be (Z)‐11‐hexadecenyl acetate and (Z)‐13‐octadecenyl acetate at a ratio of 98:2 in the Philippine blend and 1:10 in the Indian blend. Furthermore, in the field tests in Japan, neither the Philippine blend nor the Indian blend showed any attractive activity, while the Japanese blend attracted significant numbers of male moths. These results suggest that there are remarkable geographical variations in the sex pheromone composition of this species or there are several distinct species using different sex pheromone blends.

Attraction of Cnaphalocrocis medinalis (Lepidoptera: Crambidae) males in Southeast Asia to female sex pheromone traps: Field tests in southernmost China, northern Vietnam and southern Philippines with three synthetic pheromone blends regarding geographic variations

“…In the report regarding the identification of the Philippine blend, no behavioral activity has been demonstrated; only EAG activity was reported (Ramachandran et al, 1990). In our analyses, neither Z11-16:Ac nor Z13-18:Ac were detected in the crude extract of Japanese populations (Kawazu et al, 2000).…”

“…Synthetic monounsaturated aldehydes, alcohols and acetates were synthesized by Shin-Etsu Chemical Company (Tokyo, Japan). The compounds were purified by column chromatography in the same manner as reported in our previous report (Kawazu et al, 2000). Gas chromatographic (GC) analyses showed that the purified compounds contained Ͻ0.1% of the corresponding E-isomers (Kawazu et al, 2000).…”

“…The compounds were purified by column chromatography in the same manner as reported in our previous report (Kawazu et al, 2000). Gas chromatographic (GC) analyses showed that the purified compounds contained Ͻ0.1% of the corresponding E-isomers (Kawazu et al, 2000). The GC analyses were conducted on a Shimadzu GC-17A gas chromatograph equipped with an FID and a splitless injector system.…”

“…However, the former species is easily separated from the latter by a displaced post-medial line in the forewing and the lack of the harpe on the vulva (ϭspur-like projection in Bradley, 1981) seen in C. medinalis in the male genitalia (Kawazu et al, 2000), and other characteristics. C. medinalis is also distinguished from another related species, Cnaphalocrosis pilosa (Warren, 1896), in the ovate and simpler vulva, together with a straight postmedial line in the forewing.…”

“…On the contrary, a blend of a Japanese population consists of different components, (Z)-11-octadecenal (Z11-18:Ald), (Z)-13-octadecenal (Z13-18:Ald), (Z)-11-octadecen-1-ol (Z11-18:OH) and (Z)-13-octadecen-1-ol (Z13-18:OH) at a ratio of 11 : 100 : 24 : 36 (Kawazu et al, 2000). Field tests in Japan using the above three synthetic blends have shown that only the Japanese blend had significant attractiveness to male C. medinalis (Kawazu et al, 2000(Kawazu et al, , 2001(Kawazu et al, , 2002. Also, in field tests at Hangzhou in the lower Yangzhe Valley, China, with the same three blends, only the Japanese blend was significantly attractive (Kawazu et al, 2002).…”