The objective of this project is first to identify a Bacillus thuringiensis (Bt) crystal toxin with basal toxicity against Asian citrus psyllid (ACP). The toxicity of the selected toxin will then be enhanced by addition of a peptide that binds to the gut of ACP. This peptide addition to the toxin is expected to enhance both binding and toxicity against ACP. Seven Bt strains showed toxicity against ACP with significant ACP mortality at 500ug/ml relative to control treatments. One Bt strain was selected for further identification of individual toxins by LC-MS/MS analysis. Based on the results, three specific Cry toxins were identified. The identity of these toxins was confirmed by comparison with the Bt Cry toxin holotype list, using ClustalW2-nucleotide. Further ACP bioassays with two of the toxins from the selected strain indicated that both toxins show toxicity against ACP at 500ug/ml. One of these toxins was selected for modification with the gut binding peptide. A phage disulfide-constrained heptapeptide library was screened and four ACP gut binding peptides were isolated. These peptides were expressed as peptide-mCherry fusion proteins as described in the previous report. Pull down assays were used to assess the binding of peptide-mCherry fusion proteins to ACP brush border membrane vesicles (BBMV) to confirm binding and to assess the relative strength of binding of the different peptides. mCherry alone and a random sequence peptide-mCherry fusion protein were used as negative controls for these assays. Specific binding of peptides to BBMV proteins was supported by the results of binding competition assays with mCherry or with a competitive synthetic peptide. Two dimensional gel electrophoresis coupled with ligand blot analysis showed that four peptide-mCherry fusion proteins bind to 50kDa, 37kDa and 25kDa BBMV proteins all with the same pI (~9). The negative control, mCherry showed non specific binding to an abundant 50kDa protein with a pI ~5. Analysis of peptide binding to the psyllid gut in vivo using fluorescence microscopy indicated that peptide 15-mCherry and peptide 18-mCherry bind the ACP gut, with minimal background fluorescence from the mCherry negative control.