Kyung Saeng Boo, Chang Hoon Jung
Department of Agricultural Biology, College of Agriculture and Life
Sciences, Seoul National University, Suwon 441-744, Republic of Korea
The apple leaf miner, Phyllonorycter ringoniella Matsumura, is becoming a more serious insect pest on the apple trees in Korea. This is mainly due to the difficulty of theft control with insecticides, since their larvae and pupae are in apple leaf mines, and consequently their number is rapidly increasing in recent years. They have 4-5 generations a year in Korea. In order to devise a forcasting method for more accurate estimation of the* numbers and developing timings, their sex attractant, based on female pheromone components, was studied.
Their sex pheromone gland was located at the intersegmental membrane between the 8th and 9th abdominal segments of the female. The activity of both female calling and mating was mainly observed within 30 minutes after the onset of the photophase under the regimen of 16L/8D and 26 degrees C and the highest mating rate was obtained from 4-5 days old females.
The sex pheromone gland washing gave many different chemicals, but two of them, (Z)-10-tetradecenyl acetate(Z10-14:Ac) and (E,Z)-4,10-tetradecadienyl acetate (E4,Z10-14:Ac) identified with GC and GC/MS were active components in male attraction. When various ratios, from 10:0 to 0:10, of the two components, Z10-14:Ac and E4,Z10-14:Ac, were tested for their attractivity in terms of behavioral (taxis, approach and landing) response of males in a wind tunnel, the lure with 4:6 ratio elicited the highest responses in all three categories, but its activity was still below that towards a combination of two females. Even a single component Z10-14:Ac, was able to affect their taxis behavior but a combination of two chemicals was needed for their full activity.
In the field tests for the attractivity of their mixtures at various ratios in Pherocon IC traps, most of them showed a much higher activity than two virgin females. The best activity was again found in the lure baited with 4:6 ratio of Z10-14:Ac and E4,Z10-14:Ac in the years of 1994 and 1995. The same conclusion was obtained from a series of tests conducted in a net house. An isomer with one double bond, E10-14:Ac, did not improve or depress the number of catches at all, when added up to 10% of the total mixture to lures of two components at the ratio of 4:6.
This ratio is quite contrasting to those reported from Japan and China. The best ratios between the two same components, Z10-14:Ac and E4,Z10-14:Ac, were found to be 10:3 in Japan (Ujiye et al., 1986) and 7:3 LO 6:4 in China (Oku, 1993; Su & Liu, 1992), demonstrating that the one double-bond chemical is the major in these two countries but the opposite situation prevails in Korea. This is quite a peculiar case, since most of Phyllonorcycter species are known, up to now, to use the one double bond chemical, as the only one or the major chemical in those species of the genus employing this two component system (Am et al., 1992). This kind of opposite ratios in the composition of sex pheromone components was also reported from Helicoverpa assulla in Korea among Heliothis/helicoverpa species (Cork et al., 1992). Of course this latter situation concerns about at the species level, not at a geological population level of one species.
The attractivity of the lures was proportional to the total amount of the sex pheromone chemicals loaded, up to 10 ug in the wind tunnel experiment and 5mg in the apple orchard. The best efficiency of trappings were at the height of about 1.5 m above the ground and wing traps were better than either delta or water traps.
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