• Morris, O. N.
  chemical Control Research Institute, Canadian Forestry Service, Ottawa
  
• Armstrong, J. A.
  chemical Control Research Institute, Canadian Forestry Service, Ottawa
  
• Howse, G. M.
  Great Lakes Forest Research Centre, Canadian Forestry Service, Sault Ste. Marie, Ontario
  
• Cunningham, J. C.
  Insect Pathology Research Institute, Canadian Forestry Service, Sault Ste. Marie, Ontario
  

During 1972, spruce budworm infested white spruce and balsam fir trees were sprayed aerially with a low does of fenitrothion (0.25 oz AI/ac), entomopox virus (EPV) at 7.6x10^10 polyhedra/ac, nuclear polyhedrosis virus (NPV) at 2.7x10^11 polyhedra/ac, or each virus-fenitrothion combination. Fenitrothion (active ingredient), NPV, and EPV deposited at ground level at 5%, 31% and 42% respectively, of the amount emitted. In the year of application, NPV+fenitrothion was highly effective in population reduction and foliage protection especially on balsam fir. EPV + fenitrothion also provided a high level of foliage protection and apparently reduced surviving female:male sex ration to 1:2 compared with the normal 1:1 ratio. NPV + insecticide cause highest larval mortality, highest incidence of virus, lowest rate of moth emergence, fewest progeny, and lowest rate of progeny survival. The natural incidence of microsporidia was low in all plots. In the year following application, the NPV + insecticide treated plot again shared lowest population density, highest larval mortality and incidence of virus, and low defoliation and egg mass density. However, there was a higher proportion of viable eggs deposited that in the previous year. Egg parasitism by Trichogramma minuluns increased by 1.5 to 4.2% in plots treated with virus only and declined by 1.6 to 10.5% in insecticide treated plots and by 1.2% in untreated check plot. The transmission of the virus from one year to the next is considered to be of paramount importance in the future use of this pathogen in spruce budworm control.