We investigated the behavioral attractive responses of a lepidopteran larva parasite, Exorista japonica to 10 synthetic herbivore-induced plant volatiles (HIPVs). These synthetic HIPVs have been revealed the attractive effect on several parasites. For each of the HIPVs, we asked the following two questions : (1) Which volatiles show the attractiveness to this parasitoid, (2) Whether the attractant directly or indirectly affects the host settlement and parasitism of the parasitoid. To experimentally address these questions, we performed 2 and 4 choice indoor cage tests. E. japonica adults were significantly attracted to benzaldehyde and (Z)-3-hexen-1-ol showing higher settlement and parasitic rates on Spodoptera litura of treatments. Compared to the untreated plots, the average parasitism of E. japonica on S. litura larvae in the benzaldehyde treatments increased by approximately 20%.

Since first reported in 1988 the Pine Wilt Disease has been established and spreaded nearly nationwide in South Korea, causing tremendous economic damage in pine forests. The pine wilt nematode (Bursaphelenchus xylophilus), causing the Pine Wilt Disease, in Korea is known to be transported by two insect vectors that are Monochamus alternatus Hope and Monochamus saltuarius Gebler. Currently the pest management strategy largely relies on pesticide application and infected tree clearing. The aim of the present study was to search for early larval parasitoids of M. alternatus using the sentinel log infested with the cerambycid eggs. Only one braconid species was collected and identified as Spathius verustus Chao. Two to ten wasp larvae attached and fed on one host larva. Parasitism rate was 55.5 to 59 % in Jinju site, while 1 to 18.1 % the other sites. Sex ratio was female-biased (female : male = 18.9 : 1). The S. verstus has potential to be use as parasitic natural enemy of M. alternatus.

Potato tuber moth (PTM), Phthorimaea operculella (Zeller), is a serious pest of potato (Solanum tuberosum L.) plants in the fields from warm temperate to tropical climates, and tubers stored under ambient temperatures post-harvest. In recent years, concerns on PTM occurrence and damage to potato are increasing due to climate change resulted in global warming. To search potent natural enemies of PTM, we collected >150 PTM larvae from potato fields in Jeju-do in May, 2009 and then reared in the room until wasp adults emerging, which was identified by Lee J.W. as Diadegma fenestrale (tentative Korean name, 감자뿔나방맵시벌). This is the first report in Korea. When supplied 10% sugar solution on adults to rear, the longevity was 12.2±2.0 day, which was much longer than supplied with only water (5.0±1.4 day) or none (3.1±1.1 day). When the 2nd larvae of PTM, 10 days after hatch, dwelled in potato tubers were supplied to parasitoid adults for parasitization, the developmental periods from egg oviposition to adult emergence was 24.0±2.9 day, and the sex ratio of newly emerged adults was 0.27. The parasitization ratio indoor showed a kaleidoscopic characteristics, ranged from 30.0% to 71.4%. It represented that many factors might be related for the successful parasitization to PTM larvae.

The larval parasitoid, Bracon hebetor, attacks third or older larvae of indianmeal moth (Plodia interpunctella), which results in laying eggs or simply paralyzing the larvae. We studied the influence of the parasitoid’s attack on the larval development of indianmeal moth. The third larval instars of the same age were collected from the experimental colonies and each larva introduced in an acrylic cube (2 x 2 x 2 cm) treated with: 1) empty, 2) three rice grains, 3) three rice grains and a female parasitoid without ovipositor (by removing) and 4) three rice grains and a paralyzed larva. The larval activity in the experimental cube was photographed every five minutes until the larva died or pupated. Only the larvae in the cube with paralyzed larvae could pupate and emerge. The other larvae in the three treatments died before pupating, although the survival time was significantly different in relation to the treatment (F=5.27; df=2,14; P=0.019); the larvae in the empty cube had a shorter survival time than those in the rest of treatments. The results indicated that the paralyzed larvae could be fed by the health larvae and contribute to prevent population crush in the situation of food shortage with the presence of the parasitoids. The host parasitoid interaction between indianmeal moth and Bracon hebetor might not always be negative to the indianmeal moth population.

In many host-parasite interactions, intraspecific competition among host could have a significant role to the host-parasite population dynamics, yet so far a few studies has been reported theoretically and experimentally(ex. Umbanhowar and Hastings, 2002). We examined the effect of larval competition using a stage-structured matrix model with parameters estimated from the Plodia interpunctella-Bracon hebetor and Sitophilus zeamais-Aniopteromalus calandrae experimental system. The maize weevil population showed a typical growth pattern of populations with contest type competition. After introduction of A. calandrae to the system, maize weevil population was dramatically decreased to be extinct. In contrast, the Indian meal moth population showed a typical pattern of scramble type competition. Introduction of B. hebetor to the system induced higher moth density and longer persistence of the Indian meal moth population than that in the maize weevil system. These results seem to be caused by differences in intraspecific competition between Indian meal moth and maize weevil. The applications of these results should be considered in biological control of Indian meal moth.