Toxicity of the bacterial pesticidal protein Mpp51Aa1 to nymph and adult Asian citrus psyllid, Diaphorina citri

The Asian citrus psyllid (ACP), Diaphorina citri (Hemiptera: Liviidae), is a major pest of citriculture that vectors the presumed bacterial causative agent of citrus greening, Candidatus Liberibacter asiaticus (CLas). Extensive application of chemical insecticides to suppress ACP populations is the primary strategy for management of this economically important disease. The use of Bacillus thuringiensis-derived pesticidal proteins has potential as a safe and environmentally benign alternative approach for ACP management. However, lack of information on the efficacy of Bt-derived pesticidal proteins against ACP, particularly against nymphs, is a major limitation for their deployment against ACP. Here, we present the toxicity of the Bt-derived protein Mpp51Aa1 against ACP nymphs and adults. Mpp51Aa1 was expressed in the Bt strain BMB171 and purified from crystals. Protein concentration was determined by Bradford assay, and protein integrity assessed by SDS PAGE. To assess toxicity against nymphs, we developed a new bioassay method that allows nymphs to survive for up to 6 days, when maintained on treated, folded wipes (Kimtech Kimwipes). The standard hemipteran membrane feeding assay was used to assess toxicity against adult ACP. In Kimwipe assays, Mpp51Aa1 was toxic to ACP nymphs with an LC₅₀ of 56.5 µg/ml. In membrane feeding assays, Mpp51Aa1 was toxic to ACP adults with an LC₅₀ of 110.4 µg/ml. These results show that Mpp51Aa1 is toxic to both nymph and adult ACP and provides a potential alternative tool for both ACP and citrus greening management.