Heavy, natural infestation of Katahdin potatoes by the European corn borer (Pyrausta nubilalis (Hbn.)) did not affect yields of U. S. No. 1 potatoes. Five insecticides, applied as sprays, gave good control of this insect. They are: DDT, Kepone (decachlorooctahydro-l,3,4-methano-2H-cyclobuta [ed] pentalen-2-one), phosphamidon, Sevin (1 naphthyl N-methylcarbamate), and Thiodan (6,7,8,9,10,10-hexachloro-l,5,5a,6,9,9a-hexahydro-6,9-methano-2,4,3-benzodioxathiepin 3-oxide). Phorate, applied to the soil at planting time failed to give control of the borer. The green peach aphid (Myzus persicae (Sulz.)) was effectively controlled by phorate, phosphamidon, and Thiodan. Large numbers of this species occurred where DDT, Kepone and Sevin were used and may have reduced yields of potatoes on the Sevin plots. Use of heavy spray machinery on small plots reduced yields.