Insecticides to Prevent the Emergence of Scolytus multistriatus

Abstract

Emulsions of four insecticides were tested for their effectiveness in preventing emergence of the smaller European elm bark beetle, Scolytus multistriatus (Marsh.). Emulsions of 12% DDT, 6% dieldrin and 6% lindane were applied to bark brought into the laboratory. The bark surface was only slightly moistened during spraying. Lindane was most effective, followed by dieldrin and DDT in reducing emergence by 97%, 51% and 22%, respectively. Daily readings of the treatments with lindane, dieldrin, and DDT showed that 1%, 5% and 41%, respectively of the beetles were alive 24 hours after emerging. Beetles were in the larval stage at time of treatment and none of the insecticides prevented them from reaching the adult stage. Two replicated field tests were run using 0.25% to 2% sprays of DDT, dieldrin, lindane and malathion in amounts that wetted the bark of the infested elm logs. The beetles were in the larval or pupal stage when treated and again the sprays did not kill the insects until they reached the adult form. All sprays penetrated better when the bark was thoroughly wetted whereas only lindane penetrated well in the laboratory test. Lindane and dieldrin sprays at either 0.5% or 1% were very effective in reducing emergence. DDT sprays were less effective while 0.5% or 1% malathion sprays were least efficient.