Population dynamics of maize weevil, Sitophilus zeamais, and their parasitoids Anisopteromalus calandrae were examined while considering the spatio-temporal interactions using population modelling as a tool. The modelling of two species host-parasitoid systems identified the some factors concerning the long-term dynamics of interacting populations. In the single host system, the total density of S. zeamais increased exponentially and reached a saturated, asymptotic level with time. This stabilization in the density could be explained by the spatio-temporal dynamics among the patches. S. zeamais disperses continuously from patches of high density to those of low density. This density-dependent dispersal could be one of the mechanisms for stabilizing the S. zeamais population density. In the S. zeamais-A. calandrae system, both populations showed long-term coexistence. The long term coexistence could be attributed to spatio-temporal interactions of S. zeamais and A. calandrae resulted from dispersal of host and a non-random searching behavior of the parasitoid. Because such spatio-temporal variation in population dynamics, the overall host-parasitoid system may have been in a stable state, although the local population system in each patch was unstable.

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.

Dynamics of prey/host and predator/parasitoid interaction has been the main concern of the population ecology during the second half of the 20th century. Many theoretical and experimental studies have been conducted and discussed. The main questions were whether the interaction could be in stable state and whether the parasitoid/predator could regulate the host/prey populations, and if so at what levels. The questions are not yet solved, but some hypotheses have been presented that the prey/predator interaction could be in stable state, when both the predator and prey population are under intraspecific competition so that both populations could be limited at a low levels. This prerequisite, however, could not be easily satisfied in nature and several hypotheses have been discussed up to date. Biological control of pests, which is based on the predator-prey system dynamics, has not always been successful, because we do not understand the systems sufficiently. Thus, most successful cases of the biological control were dependent upon ‘trial and error’. But as the predator-prey system dynamics could be well understood in the future, more systemic control program of biological control could be possible. In this review, we analyzed the studies for biological control of pests in Korea based on 164 cases reported in the last forty years and will consider the future goal of the studies for more reliable control programs.

The effects of the genetically modified virus-resistant pepper (line: H15) and the Non-GM pepper (line: P2377) on the insect community in the pepper cultivation area were evaluated. Sampling was conducted using yellow sticky traps and pheromone funnel traps in Anseong and Deokso fields. Total number of insects caught on sticky trap were 3924 individuals at GM pepper and 3670 individuals at Non-GM pepper in Anseong and 2362 individuals at GM and 2528 individuals at Non-GM in Deokso, respectively. The total number of the insect individuals caught by sticky trap was not shown significant differences between GM and Non-GM pepper at Anseong and Deokso fields, respectively. The number of aphids per sticky trap ranged from 11.60±2.02 to 1.92±0.96 at Non-GM and from 11.56±2.15 to 0.33±0.23 at GM in Anseong, and from 2.78±1.22 to 0.11±0.08 and from 2.73±0.84 to 0.11±0.08 at Non-GM and GM pepper in Deokso, respectively. There were no significant differences in seasonal occurrences of aphids caught on sticky traps in GM and Non-GM pepper at both fields, and significant differences in aphids population density between Non-GM and GM were not observed.

The life table statistics of diamondback moth on the transgenic Chinese cabbage (line: SKCP) with myrosinase gene was compared with that on the non transgenic Chinese cabbage (line: SC) at 25±1℃. Adult life span and number of progeny of P. xylostella on the SC and SKCP lines were similar to each other. The sex ratio, developmental period, intrinsic rate of increase and finite rate of increase of P. xylostella on SC and SKCP were not significantly different in both treatments (sex rati t=-1.60; df=220; P=0.1108, developmental period: t=-0.55; df=220; P=0.5803, intrinsic rate of increase: t=-0.11; df=45; P=0.9172). However, the finite rate of increase and net reproduction were significantly different in between SC and SKCP lines (finite rate of increase: t=2.26; df=45; P=0.0287, net reproduction: t=2.08; df=45; P=0.0442). This work was supported financially by Biogreen21 project of Rural Development Administration (No. 20070301-034-010)

Effects of host density and refuge on the sex ratio of progeny of hymenopterous parasitoids was tested with Bracon hebetor Say parasitizing Plodia interpunctella (Hübner). The overall sex ratio (male/total) of progeny produced per female with and without refuge was estimated to be 0.49 and 0.41, respectively. Regardless of refuge, the sex ratio decreased as host density increased. But, at host density of 128 with refuge the sex ratio was significantly lower than that without regfuge (t=-2.17, df=24; P=0.040). The number of pupae per host larva with refuge was similar to that without refuge at the host densities tested (t=-0.10, df=53.4; P=0.921). The number of attacked host larvae showed significantly different at all host densities with and without refuge (t=-3.33, df=209; P=0.001).

The effects of the genetically modified virus-resistant pepper (line: 15, 20) and the non-GM pepper (line: 2377, 915) on the insect community in the pepper cultivation area were evaluated. Sampling was conducted using yellow sticky traps and pheromone funnel traps in Anseong and Deokso fields. Total number of insects caught on sticky trap were 3273 individuals at GM pepper and 2949 individuals at non-GM pepper in Anseong and 4357 individuals at GM and 3712 individuals at non-GM in Deokso. Total number of aphids collected on leaves were 451 and 330 individuals at GM and non-GM pepper in Anseong, respectively and 79 individuals at GM and 41 individuals at non-GM pepper in Deokso. The total number of the insect individuals caught on sticky trap was not shown significant differences between GM and non-GM pepper at Anseong and Deokso fields, respectively. Also, there were no significant differences in seasonal occurrences of aphids caught on sticky traps in GM and non-GM pepper at both fields. This work was supported financially by Biogreen21 project of Rural Development Administration (No. 20070301-034-010).

The effects of the transgenic Chinese cabbage (SKCP19 line) with myrosinase gene and Chinese cabbage (SC19 line) without gene introduction on the insect community were evaluated. Sampling was conducted using yellow sticky traps and wing pheromone traps in Anseong and Deokso fields, respectively. The total number of individuals caught by sticky trap was not shown significant differences between transgenic Chinese cabbage and non transgenic Chinese cabbage at Anseong and Deokso fields, respectively (t=0.72; df=46; P>0.05, t=0.38; df=38; P>0.05). Also, There were no significant differences in density of Plutella xylostella population caught by pheromone traps on transgenic and non transgenic cabbage at both fields (t=0.59; df=22; P>0.05, t=0.52; df=18; P>0.05). This study was funded by BioGreen21 project of Rural Department Administration (No. 20080401-034-039).

Adding cinnamon (Cinnamonum cassia Blume) extract into the adhesive used to affix stickers to a chocolate package is an effective method for protecting chocolate products from infestation by the Indian meal moth (Plodia interpunctella Hübner). Chocolate packages treated with adhesive including 0.02% and 0.025% of cinnamon extract were not infested with the Indian meal moth for up to 30 days at 28.1℃ and 70-75% RH, whereas 100% of the packages without the extract were infested in the no-choice test. Chocolate packages treated with adhesive including 0.02% and 0.025% of cinnamon extract in the quadruple choice test were not infested with the Indian meal moth for up to 60 days at 28.1℃ and 70-75% RH, whereas 100% of the packages without the extract were infested. A panel test showed that the cinnamon extract treatment would not affect consumers’ choices.

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.

대용량 밀 저장 엘리베이터(직경 8 m, 높이 41 m)에서 화랑곡나방(Plodia interpunctella ())의 유충기생봉, Bracon hebetor Say, 방사를 통한 화랑곡나방 개체군의 억제 실험을 수행하였다. 2002 년 7월 23일부터 일주 간격으로 총 50,000 마리의 기생봉을 방사하였던 바 화랑곡나방 성충의 밀도 수준이 방사하지 않은 엘리베이터에 비해서 30% 수준으로 유지되었다.