Provided is a peptide, peptide multimer or fusion protein containing such peptide which binds to the gut of sap-sucking insects, e.g., aphids. When bound, this peptide inhibits the binding of targeted virus to the insect gut. When this peptide or tandem repeat peptide is expressed (or is expressed as part of a fusion protein) in the fluids of transgenic plants, it is taken up by the insect with the sap, binds to gut receptors and thereby inhibits transmission of the virus from plant to plant via the insect vector. Thus, the use of such transgenic plants blocks or reduces the transmission of the targeted virus and others which share the peptide binding site within the insect gut among plants susceptible to the virus and thereby reduces losses due to viral infection.