좁은가슴잎벌레는 십자화과작물을 가해하는 해충으로 알려져 있다. 본 연구는 온도가 좁은가슴잎벌레의 발육단계별 발육기간, 성충의 수 명과 산란특성에 미치는 영향을 파악하고자 성충 전 발육단계는 15, 20, 25, 27.5°C에서, 성충은 10, 15, 20, 25, 27.5°C 항온조건에서 조사하였 다. 알과 유충은 항온조건에서 다음 발육 단계로 성공적으로 발육하였다. 알, 유충, 번데기의 발육기간은 온도가 상승할수록 짧아지는 경향을 보 였다. 좁은가슴잎벌레의 발육영점온도, 유효적산온일도는 선형회귀분석을 통해 추정하였으며 알에서 성충출현까지 발육영점온도와 유효적산온 일도는 8.7°C와 344.73DD였다. 좁은가슴잎벌레 발육단계별 최저, 최고 온도의 한계는 Briere함수를 이용하여 추정하였으며 알에서 성충출현 까지 최저, 최고한계는 5.3°C와 40.4°C였다. 성충은 10°C와 27.5°C 범위에서 산란이 가능하였고 21.7°C에서 최대 약 627.5개의 알을 낳는 것 으로 추정되었다. 노화율, 나이별 생존율, 나이별 누적산란율, 온도의존 산란수와 관련된 성충모델들을 작성하였다. 본 연구에서 제시한 온도발육 모형과 성충산란모형은 좁은가슴잎벌레 개체군동태를 이해하는데 유용할 것이며 십자화과작물의 종합적 해충군관리체계를 마련하는데 기초자 료로 활용될것으로 기대된다.

좁은가슴잎벌레의 각 태별 발육기간은 25℃에서 알기간 6.8일, 유충기간 1령 2.4일, 2령 2.2일, 3령 5.4일, 번데기기간 4.1일로 알부터 번데기까지의 기간은 20.6일이 소요되었다. 유충 및 번데기 발육기간 중 생존율은 25℃에서 1령 유충은 87.5%이고 2령, 3령유충과 번데기는 83.3%가 생존하였다. 성충의 산란과 수명은 25℃에서 산란전기간 10.6일(6 ∼10일), 산란기간 130.6일(13∼269일), 산란수 566.4개(13∼1,237개), 성충수명 189.0일(25∼365일)이었다. 또 성충의 최대 산란기간이 10, 15, 20℃에서 각각 650, 682, 402일로 매우 길었으며 산란기간 동안 일정한 시기에 산란수가 없거나 급격히 낮아지는 기간이 나타나는 생리적 현상에 대하여 보다 정밀한 추가 구명이 필요하다.

Integrin is a heterodimer protein that locates on cell membrane to interact with neighboring cells or extracellular matrix. A transcriptome analysis of the brassica leaf beetle, Phaedon brassicae, midgut identified both α and β subunits of integrin. RNA interference of β subunit genes significantly impaired survival of both larvae and adults of P. brassicae. A recombinant bacteria expressing double-stranded RNA specific to β integrin of P. brassicae were constructed and showed significant oral toxicities.

Cabbage is one of the major vegetable crops especially in Korea. Various insect pests intimidate the cabbage production. Moreover, an excessive spray of chemical insecticides leads to development of insecticide resistance as well adverse effects on environment and humans. The brassica leaf beetle, Phaedon brassicae, is a coleopteran pest. Both larval and adult stages feed cabbage. This study aimed to develop an effective microbial biopesticide against P. brassicae by adding immunosuppressive agent to Bacillus thurigiensis (Bt). To determine an optimal immunosuppressive agent, two bacterial species of Photorhabdus temperata subsp. temperata (Ptt) and Xenorhabdus nematophila were compared in their insecticidal activity against P. brassicae, and Ptt was selected. Among four subspecies of Bt, B. thuringiensis subsp. tenebrionis (Btt) was selected. Ptt bacterial culture broth possessed immunosuppressive agent(s) because the bacterial culture broth significantly increased other bacterial growth in P. brassicae hemolymph. When the Ptt broth was added to Btt, it significantly increased the insecticidal activity of Btt. Bt-Plus was prepared by mixing Btt and Ptt bacterial culture and sprayed the cabbage infested by P. brassicae. The Bt-Plus was much more effective than Btt treatment. This study reports a novel Bt insecticide to control P. brassicae.

A new gregarine species (Eugregarinida: Gregarinidae) was previously reported from daikon leaf beetle, Phaedon brassicae at Daegwallyeong in Korea. Here, we found another novel gregarine species from the striped flea beetle, Phyllotreta striolata (Coleoptera: Chrysomelidae). This paper describes the morphological and molecular-biological characteristics of Gregarine species associated to P. brassicae and P. striolata. The size and body shape at mature trophozoite stage were the main diagnostic characteristics of those species. Gregarines from P. brassicae were bigger size (100um) with square shaped body while Gregarines from P. striolata were slightly smaller size (80um) with egg shaped body. Based on the partial 18S rDNA sequence, gregarine species from P. striolata was grouped in eugregarine and also this new gregarine showed 85% homology that of the reported Gregarina sp. from P. brassicae. However, gut dissection result showed that each species had own gregarine parasite species association. These results were identical in local populations from three surveyed locations. There was positive relationship between infection rates and elevation for gregarine related to P. striolata. Therefore, we suggested that the gregarines and their coleopteran hosts have species-specific interaction via co-evolution.

A gregarine parasite (Apicomplexa: Protozoa) was observed in the population of daikon leaf beetle, Phaedon brassicae Baly, (Coleoptera: Chrysomelidae) in Daegwallyeong. Gregarines are well known species-specific parasites of various Arthropoda. Based on 1.727kb of 18S rDNA sequence (FJ481523), this gregarine species was grouped in eugregarine and 5.258kb of full length rDNA replicon was cloned. We also observed interaction of tropozoite or gamonto of gregarine and epithelium of host midgut using scanning electron microscope. Although development of the infected host delayed half day in every larval stage, there was no significant difference in the development of daikon leaf beetle whether it is infected or not. Therefore, this gregarine parasite is not promising candidate for bio-insecticide in daikon leaf beetle.

Gregarine parasite (Apicomplexa: Protozoa) was observed in the population of daikon leaf beetle, Phaedon brassicae Baly (Coleoptera: Chrysomelidae) in Daegwallyeong. Morphological features of the gregarine in gut of P. brassicae have been studied by light microscope and scanning electron microscope with particular attention to the relationship between the epimerite and the host epithelium. On the average of mature trophozoite length and width are 100 and 40㎛, respectively. Based on 1.727kb of 18S rDNA sequence, this gregarine grouped in eugregarine.