Abstract: Pathogenic effector proteins which include one or more RxLR, dEER, Pexel or analogous motifs are blocked from entry into plant or animal cells by binding one or more of the motifs with a blocking compound which prevents binding of phosphoinositides or other polar lipids to the motifs which is a prerequisite for translocation of the pathogenic effector proteins into the plant or animal cell. The blocking compounds can take a variety of forms including synthetic peptides or the hydrophilic head-groups of phosphoinositides, phosphatidic acids, phospholipids, or sphingolipids. Suitable blocking compounds can be identified by assays demonstrating binding to RxLR, dEER, Pexel or analogous motifs. In addition, pathogenic effector proteins can be identified by analyzing whether they contain structural RxLR motifs using hidden markov modeling.