Corynespora cassiicola leaf disease is a serious threat to rubber trees; the fungus infected leaves develop necrotic lesions and abscind, leaving the tree unproductive. The destructiveness of C. cassiicola has been largely attributed to cassiicolin, a host-selective protein toxin secreted by the fungus. Recombinant antibody technology offers hope to curtail the disease; single chain variable fragment (scFv) specific to cassiicolin could bind and deactivate the toxin in genetically modified rubber trees that harbour the antibody gene. Anti-cassiicolin scFv phage library was constructed from cassiicolin immunized Balb/C mice spleen IgG heavy and light variable chains. Biopanning of the phage library yielded a scFv clone with high specificity to cassiicolin. The nucleotide sequence and deduced amino acid sequence information of the scFv were obtained. The hemagglutinin (HA) tagged scFv expressed in Escherichia coli is discerned as a band at circa 30 kDa on SDS-PAGE. The corresponding band was detected by anti-HA IgG on a Western immunoblot of the gel. Deactivation of cassiicolin by the scFv was demonstrated by leaf bio-assay on PB 260, a susceptible clone. Leaf bioassay is in progress to evaluate deactivation of cassiicolin on the other susceptible clones that are also amenable for genetic modification i.e. GL 1, RRIM 600 and BRIM 2020.