how do monoclonal antibodies help controlling plant disease?

Monoclonal-- Genetically engineered antibodies specific for one antigen.

Monoclonal antibodies (mAb or moAb) are monospecific antibodies that are made by identical immune cells that are all clones of a unique parent cell, in contrast to polyclonal antibodies which are made from several different immune cells. Monoclonal antibodies have monovalent affinity, in that they bind to the same epitope. Given almost any substance, it is possible to produce monoclonal antibodies that specifically bind to that substance; they can then serve to detect or purify that substance. This has become an important tool in biochemistry, molecular biology and medicine. When used as medications, the non-proprietary drug name ends in -mab (see "Nomenclature of monoclonal antibodies"), and many immunotherapy specialists use the word mab anacronymically.

monoclonal antibodies

Monoclonal antibodies are commonly used to fight a large number of diseases including cancer. The monoclonal antibodies fight the disease by targeting a certain antigen and recruiting the body's natural immune system to destroy the antigen-infected cells.