Se-Jin Kim

Sex Pheromones and Reproductive Isolation in Five Mirid Species

Mate location in many mirid bugs (Heteroptera: Miridae) is mediated by female-released sex pheromones. To elucidate the potential role of the pheromones in prezygotic reproductive isolation between sympatric species, we investigated differences in the pheromone systems of five mirid species, Apolygus lucorum, Apolygus spinolae, Orthops campestris, Stenotus rubrovittatus and Taylorilygus apicalis. GC/MS analyses of metathoracic scent gland extracts of virgin females showed that all five species produced mixtures of hexyl butyrate, (E)-2-hexenyl butyrate and (E)-4-oxo-2-hexenal, but in quite different ratios. (E)-2-hexenyl butyrate was the major component of A. spinolae, while hexyl butyrate was the most abundant component in the pheromone blends of the other four species. In addition to the three compounds, a fourth component, (E)-2-octenyl butyrate, was present in the gland extracts of A. lucorum and T. apicalis females. Field tests suggest that the ternary blends of hexyl butyrate, (E)-2-hexenyl butyrate and (E)-4-oxo-2-hexenal as found in the extracts of the females of each species do not inhibit attraction of conspecific males but ensure species-specificity of attraction between A. lucorum, O. campestris and T. apicalis. Furthermore, (E)-2-octenyl butyrate was essential for attraction of A. lucorum and T. apicalis males, but strongly inhibited attraction of male A. spinolae, O. campestris and S. rubrovittatus. The combined results from this study and previous studies suggest that the minor component and pheromone dose in addition to the relative ratio of the major components play an important role in reproductive isolation between mirid species.

Hatchability and Temperature-dependent development of Overwintered Eggs of Ricania sp. (Hemiptera: Ricaniidae)

Ricania sp. lay eggs into the new twigs of blueberry and suck nutrients causing growth retardation and a sooty mold symptom. This study was conducted to investigate the emergence success and developmental period of overwintered eggs of Ricania sp. under the seven constant temperatures from 10 to by intervals (14L:10D). We also monitored the emergence time of the Ricania sp. nymph at blueberry by 3 ~ 4 day interval using a modified leaf clip cage. Development times from the overwintered egg to nymph were 107.1, 54.5, 33.9, 25.3, 25.1 and 16.7 days and the emergence successes were 23.1, 30.8, 13.8, 21.7, 11.9, and 0.6% at 14, 18, 22, 26, 30 and , respectively except at . The developmental periods were decreased with increasing temperatures. First emergence date of the nymphs in the field was between 19 and 22 May, and the average emergence success was 19.6%. The present study might be helpful to establish the management strategy of Ricania sp. based on the biological characteristic.

Host Plant, Occurrence, and Oviposition of the Eurytomid wasp Eurytoma maslovskii in Korea

We investigated the host fruit, seasonal occurrence, and oviposition habits of the eurytomid wasp, Eurytoma maslovskii that cause Japanese apricot fruit drops. This eurytomid wasp was found to occur in Gyeonggi-do, Chungcheongbuk-do, Chungcheongnam-do, Jeollanam-do, and Jeollabuk-do in Korea, and it attacked seeds of Japanese apricot, apricot, and peach. Overwintered larvae were observed until mid April, inside the stone of Japanese apricots. Pupation took place between late March and late April. More than 90% of the adult wasps emerged between late April and early May. The female wasps laid eggs just under the seed coat before endocarp hardening. The length of the wasp ovipositor was at least 5 mm, and hence, the diameters of fruits for oviposition would not exceed 2 cm. We observed up to five eggs per fruit, and the egg stage did not last for more than two days. Newly hatched larvae moved to the embryo, which is the first part that forms in a seed, and feeds on this. Larval competition occurs during this time; in this study, only one larva survived and matured. Thus, from the larva cycle of the wasp, most of the damaged fruits would have fallen by early June, before the harvest period.

Development and characterization of 12 microsatellite loci from the blueberry gall midge Dasineura oxycoccana (Diptera: Cecidomyiidae)

The blueberry gall midge, Dasineura oxycoccana (Johnson), is a serious insect pest of blueberries and cranberries in North America. In this study, we developed 12 novel microsatellite loci for this gall midge. To obtain its sequence data, next-generation sequencing was performed using mixed individuals collected from Korea and the USA. The developed loci were polymorphic, with four to nine alleles in 20 individuals from a single population of New Jersey, USA. The analyses revealed that all 20 individuals had different multilocus genotypes with expected heterozygosity ranging from 0.708 to 0.920. In addition, we confirmed the discriminative resolution of all individuals collected. These markers will facilitate future studies on the genetic structure of blueberry gall midge populations.

Reproduction and Parasitization Capacity of an Insect Parasitic Mite, Pyemotes moseri Yu et Liang (Acarina: Pyemotidae) New to Korea

An insect parasitic mite was found on a larva from Japanese apricot seed. The mite was identified as Pyemotes moseri Yu et Liang (Acarina: Pyemotidae) new to Korea. The host larva was identified as Eurytoma maslovskii using mitochondrial DNA sequencing analysis. We conducted preliminary study on its reproduction and parasitization capacity in laboratory condition. A mated female mite reared on Eurytoma maslovskii larva. We counted and sexed newborn progenies and then eliminated them during periodical observations. To test parasitization capacity, a PCR tube containing mass reared P. moseri and Japanese apricot seeds (assumed bear larva of E. maslovskii) placed in a stainless bath filled with potting soil. One month later, we surveyed the seeds whether the E. maslovskii larva parasitized by mite or not. We repeated this experiment three times with five replications each. Average life span (days from parasitization to the end of reproduction) of gravid females was 24.4 days (n=8). A gravid female reproduced 104.0 female progenies (n=8). Although there were more than seven Japanese apricot seeds per bath containing larva or pupa, we found parasitization only in two seeds.

A Report on the Control Effects of Automatic Dry Fog Sprayer on Aphids in Greenhouse Crops

The area of greenhouse horticulture has increased dramatically since the early 1990s in Korea. However, area per farmer still very small and diverse pest species occurs in greenhouse abundantly because of its protected condition. To manage pests, farmers use many pesticides frequently. Incessant and improper use of chemicals provoked pesticide resistance in pest and poisoning of farmers. In this study, we investigated the efficiencies of automatic dry fog sprayer for controlling two aphid species, Aphis gossypii and Myzus persicae, in greenhouse horticulture. When doors and side windows were completely closed in automatic dry fog sprayer treatment greenhouse, aphids were controlled similar level with conventional spraying method (percent control: 61.0~94.1%). However, when half of the doors and side windows of the greenhouse were opened, aphids were controlled poorly (percent control: 36.0~54.4%).