Kyung San Choi

Sex pheromone production and response in Korean populations of the diamondback moth, Plutella xylostella

The diamondback moth, Plutella xylostella (L.) (Lepidoptera: Yponomeutidae), is a worldwide pest of cruciferous crops. We examined the female pheromone production and male response to various pheromone blends in two Korean populations. Gas chromatography (GC) and GC‐mass spectrometry (MS) analyses of pheromone gland extracts revealed that females produce (Z)‐11‐hexadecenal (Z11‐16:Ald), (Z)‐11‐hexadecenyl acetate (Z11‐16:OAc), and (Z)‐11‐hexadecen‐1‐ol (Z11‐16:OH) in a ratio of 8:100:18. However, (Z)‐9‐tetradecenyl acetate (Z9‐14:OAc), a previously reported component of the sex attractant of a Canadian P. xylostella population was not detected in gland extracts of the Korean one. Field tests showed that Z11‐16:Ald and Z11‐16:OAc are essential for attraction of male moths, and the highest attraction is obtained with a 10:90 blend mimicking the blend found in gland extracts. Addition of 1 or 10% of Z11‐16:OH to the 10:90 blend of Z11‐16:Ald and Z11‐16:OAc significantly increased attraction. However, attraction was strongly antagonized by the addition of as little as 0.1% of Z9‐14:OAc to the most attractive ternary blend. The ternary blend of Z11‐16:Ald, Z11‐16:OAc, and Z11‐16:OH at a ratio of 10:90:1 was more effective at catching P. xylostella males than the Japanese three‐component blend or the Canadian four‐component blend in Korea. These results suggest that there is geographical variation in the pheromone systems of this species.

Seasonal Development and Population Fluctuations of Arrowhead Scale, Unaspis yanonensis (Homoptera: Diaspididae), in Citrus orchards in Jeju, Korea

Abstract Arrowhead scale, Unaspis yanonensis (Kuwana), feeds on the foliage, stems, and fruits of citrus trees, and causes tree dieback when heavy infestations occur. The objective of this study was to collect basic data to establish seasonal management strategies for U. yanonensis. The abundances of male nymphs and female adults were monitored in unsprayed citrus orchards. The overwintered females started to produce their progenies (1st gen.) from mid-May. The populations of the 1st nymphs in the 1st generation showed a bimodal occurrence pattern, with a 1st larger peak between late May and early June, and a 2nd smaller peak in June. The nymphs in the 2nd generation, which were laid from newly developed females, were observed from late July, and the 1st peak occurred in mid-August, followed by an obscure later peak (the 2nd peak) around late September. The numbers of live females for the overwintered populations began to decrease gradually from early June by the impact of the predacious Chilocorus kuwanae, as well as by natural mortality factors, and dropped to a low level in mid-July. When there were abundant predator attacks, the U. yanonensis female populations sharply decreased from early June and were almost nonexistent in July. New female adults (1st generation adults) appeared from late June and peaked in mid-July. The 2nd generation female adults, consequently, the overwintering generation, occurred from mid- September, and gradually increased to late October. Overall, these results will be useful in terms of management strategies for U. yanonensis in citrus orchards.

Development of Sex Pheromone Trap for Monitoring Matsumuraeses falcana (Walshingham) (Lepidoptera: Tortricidae)

Abstract This study was carried out to find out an effective formulation for monitoring the soybean podborer, Matsumuraeses falcana (Walshingham), using its sex pheromone in Korea. A 1 : 1 : 1 mixture of (E)-8-dodecenyl acetate (E 8–12: Ac), (E,E)-8,10-dodecadienyl acetate (E 8 E 10–12: Ac) and (E,Z)-7,9-dodecadienyl acetate (E 7 Z 9–12: Ac) was an effective composition in monitoring M. falcana. A binary mixture of E 8–12: Ac and E 8 E 10–12: Ac was essential to attract M. falcana male moths. E 7 Z 9–12: Ac showed a synergistic effect on the attractiveness of 1 : 1 mixture of E 8–12: Ac and E 8 E 10–12: Ac. These chemicals alone showed little or no attractiveness to M. falcana. The sticky-typed wing trap baited with sex pheromone captured significantly more males than the water-pan trap. Trap catches within a soybean field were much more than those in perimeter trap. The trap-baited with sex pheromone gave a distinct fluctuation pattern of male catches throughout the flight seasons. Therefore, it can be expected that pheromone-baited trap provides a simple tool for monitoring the soybean podborer, M. falcana in Korea.

(E)-5-Hexadecenyl Acetate: A Novel Moth Sex Pheromone Component From Stathmopoda auriferella

The sex pheromone of Stathmopoda auriferella (Walker), an important pest of kiwifruit in Korea, was studied. Two candidate pheromone components detected in the gland extracts of females were identified as (E)-5-hexadecenyl acetate (E5-16:OAc) and (E)-5-hexadecenol (E5-16:OH) in a ratio of 75:25 by mass spectral analysis of natural pheromone components and dimethyldisulfide adducts, and retention index comparisons with synthetic standards. In the kiwifruit orchards, E5-16:OAc alone was attractive to S. auriferella males and caught significantly more males than live virgin females. However, addition of E5-16:OH strongly inhibited attraction to E5-16:OAc. These results suggest that the major component of the female-produced sex pheromone of S. auriferella is E5-16:OAc. This hexadecenyl acetate is a novel moth sex pheromone component.

Elevated CO2 may alter pheromonal communication in Helicoverpa armigera (Lepidoptera: Noctuidae): Elevated CO2 and moth communication

Carbon dioxide (CO2) as a greenhouse gas has been increasing in recent decades. Because an elevated atmospheric CO2 influences insect physiology and behaviour, we hypothesize that pheromone–mediated communication in the moth is affected by an increased CO2 level. We test the behavioural responses of male Helicoverpa armigera to sex pheromone in a wind tunnel, demonstrating a significant reduction of approaching behaviour to the odour source at a high CO2 level (1000 ppm). Electroantennogram (EAG) responses of male to the pheromone component are also significantly suppressed in high CO2 environments (600 and 1000 ppm), indicating that a high CO2 level inhibits both behavioural and electrophysiological responses of male to the sex pheromone. Interestingly, the EAG response of the whole head preparation of males is influenced more by the elevated CO2 level than that of the antenna‐cut preparation. A sequential increase of CO2 levels from an ambient CO2 level also decreases the EAG response of the whole head but not of the labial palp‐removed head, implying a potential mediation of labial palp in the head where the CO2 receptor is located. By contrast, sex pheromone production in females reared under or shifted to an elevated CO2 condition is increased, and the putative underlying mechanism for this is discussed. The present study provides an insight into the adaptive strategy of moth pheromone communication in a changing environment.