A Novel Formulation ofBacillus thuringiensisfor the Control of Brassica Leaf Beetle,Phaedon brassicae(Coleoptera: Chrysomelidae)

Abstract

Cabbage is a major vegetable crop over the world. Various insect pests can affect cabbage production. Excessive spray of chemical insecticides can lead to the development of insecticide resistance with various adverse effects on the environment and humans. Brassica leaf beetle, Phaedon brassicae Baly, is a coleopteran pest. Both larvae and adults cause damages to cabbage. The objective of this study was to develop an effective microbial insecticide against P. brassicae by adding an immunosuppressive agent to Bacillus thuringiensis (Bt). The immunosuppressive agent was chosen from bacterial cultured broth of Photorhabdus temperata subsp. temperata (Ptt). Reverse phase HPLC revealed that Ptt-cultured broth possessed at least two eicosanoid biosynthesis inhibitors (oxindole and indole) in its hexane extract. The bacterial cultured broth exhibited potent immunosuppressive activity against P. brassicae. Based on toxicity results, B. thuringiensis subsp. tenebrionis (BtT) was selected from four strains of Bts. When Ptt-cultured broth was added to spore-producing BtT cells, the insecticidal activities of BtT against both larvae and adults of P. brassicae were significantly increased. This bacterial mixture applied to develop a "Bt-Plus," which was formulated by mixing BtT cells (10(11) spores per ml) and 48-h Ptt-cultured broth along with additives (surfactant and preservative). When Bt-Plus was sprayed to cabbage infested by P. brassicae at 1,000-fold dilution, the mixture exhibited much higher control efficacy than BtT treatment alone, suggesting it could be used as a novel Bt insecticide for the control of P. brassicae.

Dual Oxidase-Derived Reactive Oxygen Species Against Bacillus thuringiensis and Its Suppression by Eicosanoid Biosynthesis Inhibitors

“…Moreover, BZA identified from Ptt culture broth (Seo et al, 2012) can also significantly enhance BtK virulence. All these observations support the practical application of Ptt culture broth to effectively control P. xylostella by mixing Bt insecticides in a form of Bt-Plus (Kim et al, 2015).…”

Proceedings of the 5th International Symposium on Biological Control of Arthropods, Langkawi, Malaysia, September 11-15, 2017

“…The Btt isolate expresses the proteins Cry3 and Cyt2 (Crickmore, 2016), normally used in bioinsecticide formulations to control Coleoptera in agriculture and forestry (Elek and Beveridge, 1999;Whiters et. al., 2013;Kim et al, 2015). The pathogenicity of Bti and Btt isolates shows possibilities for eucalyptus snout beetle management, as new specific bioinsecticides.…”

The great potential of entomopathogenic bacteria Xenorhabdus and Photorhabdus for mosquito control: a review

“…Such metabolites have also been reported as potentiators of toxicity of B. thuringiensis against lepidopterans and coleopterans, acting in suppressing the immune response of these insects. [109,141]. In cultures of X. nematophila and P. temperata temperata, seven metabolites with the function of inhibiting phospholipase A 2 were identified [138].…”

“…In the context of mosquito control, several analyses were made aiming the establishment of new effective agents such as: (i) mixture of the culture broth of P. temperata temperata with B. thuringiensis tenebrionis, called "Col-Kill", demonstrated efficacy in the control of the coleopteran Phaedon brassicae [141]; (ii) for the control of lepidopteran Plutella xylostella and Spodoptera exigua, the mixture called "Dual Bt-Plus" by B. thuringiensis kurstaki and B. thuringiensis aizawai with culture broth X. nematophila [155]; and (iii) some authors described the ability of Xenorhabdus and Photorhabdus bacteria to increase the toxic effect of Cry4Ba derived from Bti against Ae. aegypti [29,64].…”