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A Novel Bt-Plus Development to Control the Brassica Leaf beetle, Phaedon brassicae
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.
