In 11 experiments insecticides were screened as foliage sprays for insecticidal activity against the potato leafhopper, Empoasca fabae (Harr.), on Irish potatoes. Four weekly applications of Dc1nav@ (2, 3-p-dioxanedithiol s, s-his(O,O-diethyl phosphorodithioate). Sevin@ (l-naphthvl-N-methyl carbamate), and Thiodan @ (6,7,8,9,10,10-hexuchloro-l,5,.5a,6, 9,9a-hexahyd ro-6,9- methano-2,4,3-benzodioxathiepin-3-oxide) at dosages as low as 0.2 pound per acre were still highly effective 7 days after the last treatment, showing a 98% reduction in leaf hoppers at that time. Ethion, Guthion (O,O-dimethyl S-(4-oxo-3ll-1,2,3-benzotriazine- 3-methyl) phosphorodithioate), and Trithion@ (S-(p-chlorophenylthio) methyl O,O-diethyl phosphorodithioute) gave good results at 0.5 pound actual per acre. Diazinon@ (O,O- diethyl O-(2-isopropyl-4-lnethyl-6-pyrimidinyl) phosphorothioute), Dihroll@ (O,O-dimethyl-O-(l, 2,-dibromo-2,2-dichloroethyl phosphate), Dipterex@ (O,O-dimethyl 2,2,2-trichloro-l-hydroxy-ethylphosphonate), parathion, and Phosdrin'@ (l-methyloxycarhonyl- I-propen-2-yl dimethyl phosphate, 60% technical) applied at 0.5 pound actual per acre produced a high initial mortality but afforded only a limited residual action. DDT at 0.5 pound actual was quite effective but was inferior to Sevin, Thiodan, and a DDT-Dibrom combination. Aldrin, dieldrin, ami heptachlor did not give adequate leafhopper control. Observations in commercial plantings showed that damage by the potato tuber worm, Gnorimoschema operculella (Zell.), to tubers in the soil was directly influeneed by the degree of potato leaf hopper control and the potato variety. '11ere poor leafhopper control was obtained 63% of the Cobbler tubers were infested with tuber worms as compared with an infestation of only 1.5% in the Pungo variety. Tuber worm damage to Cobbler tubers was very light in fields receiving adequate leaf hopper protection.