In Idaho tests, Dyfonate and Thimet gave the best control of all the compounds tested. For best results, they should be applied when the soil contains between 50 and 70 percent of its water holding capacity and the temperature is above 50 degrees Fahrenheit. Colorado Potato Beetle eggs are laid in groups on the undersides of leaves. Control treatments should be applied after most of the eggs have hatched but before serious plant damage occurs. Treat infestations with permethrin, Ambush, endosulfan, Sevin, Guthion, Monitor or Imidan.
Thorough coverage is important.
Currently, no soil insecticides are registered for White Grubs on potatoes. Symphylan infestations are still another problem. They can scar the surface of tubers. High quality potatoes are seldom produced in infested soils. Garden symphylan numbers may be reduced by mixing parathion or Dyfonate into the soil in the spring as suggested for wireworm control.