NEMATODE CONTROL OF BLACK ARMY CUTWORM (LEPIDOPTERA, NOCTUIDAE) UNDERLABORATORY AND FIELD CONDITIONS

Four steinernematid strains, Steinernema carpocapsae All strain, S. ca rpocapsae Umea strain, S. feltiae L1c strain, and S. feltiae strain 27 , were evaluated in laboratory and field tests as potential agents for the control of the black army cutworm, Actebia fennica (Tauscher). Al though each of the six instars was susceptible to attack, incidences o f infection were highest and generally over 60% for the third, fourth, and fifth instars when exposed to 100 infective juvenile nematodes in petri dishes. Fifth-instar larvae exposed for 1 week to soil containi ng 4000 infective juveniles in a 1:1:1 mixture of the Lie, All, and Um ea strains were most frequently infected with the Lie strain when rear ed at 10 and 12 degrees C and with the All strain when reared at 14 an d 16 degrees C. One hundred thousand infective juveniles of the Lie, A ll, and Umea strains and strain 27, alone and in various combinations, and applied by either a spray or soil-plug inoculation, killed black army cutworm larvae caged in the field for 1 week with treated black s pruce seedlings and provided protection of current and 1-year-old foli age. Treatments that included strain 27 provided the best protection w hen daily mean soil temperatures were 7-11 degrees C in comparison to treatments that included the Umea or All strains, whereas treatments t hat included the All strain as a component appeared to be more effecti ve than treatments containing the Lie and Umea strains when daily mean soil temperatures were 16-17 degrees C.