• Kaupp, W.J.
  
• Cunningham, J.C.
  
• Howse, G.M.
  
• McPhee, J.R.
  
• Groot , P. de
  

Thee plots, containing mainly white spruce, Picea glauca (Moench) Voss, with total area of 120 ha, were sprayed with nuclear polyhedrosis virus when larvae of the spruce budworm, Choristoneura fumiferana (Clem), were in the needle-mining second instar.  Aerial applications were made at 9.4 l/ha with a virus dosage of 125 billion polyhedra/ha. The aqueous formulation contained 250 ml/l molasses, 60 g/l IMC 90-001 sunlight protectant and 1.25ml/l Chevron sticker. Two of the plots receives a second application 6 days later with the same dosage and formulation.

Levels of virus infection and subsequent mortality were lower than those recorded following virus application on later instars in previous years. The double application gave better larval infection than the single ut was still unsatisfactory.  It is concluded that the second instar, although highly susceptible to nuclear polyhedrosis virus, is not the best state of insect development for virus application with the formulation currently available.