The toxicity of Bacillus thuringiensis bio-insecticidal proteins, Mpp51Aa1 and Cry1Ba1, against the healthy and Candidatus Liberibacter asiaticus-infected Diaphorina citri

Diaphorina citri Kuwayama (Hemiptera: Liviidae), is a threatening citrus pest worldwide, it transmits the bacterium, ‘Candidatus Liberibacter asiaticus’ (CLas), causing citrus greening disease. Insecticides are the main control strategy for limiting D. citri. the widespread usage has increased the resistance of D. citri to insecticides. The pesticidal proteins from Bacillus thuringiensis (Bt) are active against insects and provide a sustainable approach to insect control. We investigated the impact of CLas infection of D. citri on the toxicity of two Bt-proteins (Mpp51Aa1 and Cry1Ba1). Proteins were delivered to healthy and CLas-infected D. citri via topical feeding application. The LD₅₀ values of Mpp51Aa1 and Cry1Ba1 were calculated for both nymphs and adults. We evaluated the effect of each protein on the survival probabilities and lifespan of D. citri. LD₅₀ values indicate that adults and nymphs were more susceptible to Mpp51Aa1 than to Cry1Ba1 in both healthy and CLas-infected D. citri. CLas-infected D. citri adults and nymphs were more susceptible to Mpp51Aa1 and Cry1Ba1. D. citri nymphs were more susceptible to Mpp51Aa1 and Cry1Ba1 than adults. We found that Mpp51Aa1 had a greater impact on the survival and lifespan of adults, and CLas-infected insects were more affected by these pesticidal proteins. These findings are useful for the use of pesticidal proteins in D. citri management given the widespread presence of CLas in the D. citri population. In this era of eco-friendly control strategies, pesticidal proteins provide a new avenue to reduce the application of chemical insecticides.