KNACK (pyriproxyfen) is an insect growth regulator (IGR) which is being developed in the United States for control of silverleaf whitefly, Bemisia argentifolii, (SLWF) in cotton. KNACK acts as a juvenile hormone mimic and causes inhibition of metamorphosis, embryogenesis, reproduction, and larval development in certain insects. In SLWF, KNACK inhibits egg hatch, either through the females or by direct contact with the egg, and suppresses adult emergence when larvae stages are affected. KNACK also exhibits pronounced translaminar movement in cotton leaves which also leads to inhibition of egg hatch and suppressed adult emergence after SLWF feeding on the lower leaf surface.