• Otvos, Imre S.
  Newfoundland Forest Research Centre
  
• Moody, B.H.
  Newfoundland Forest Research Centre
  

Spruce budworm infestations on the Island have been recorded since 1942. Infestations prior to the present outbreak were small, lasted only a few years, and collapsed without causing significant damage. The collapse of these infestations was caused by natural factors such as weather, parasites, and disease and starvation.

The present outbreak started in 1971, and is unprecedented in size and intensity; in 1977 it covered about 90% of the productive forests of the Island and caused an estimated 5,100,000 m3 of tree mortality. The impact of the budworm on the forest cannot be fully assessed at this time as  the outbreak is in progress and trees will continue to die for at least 3 years after the outbreak has collapsed.

The biology and habitats of the budworm in Newfoundland are similar to those in other areas of eastern North America except development in Newfoundland throughout the life cycle is delayed by 2-3 weeks and a much lower proportion of larvae mines the older needles. Among the natural control factors of the spruce budworm in Newfoundland probably weather is the most important. Other control factors such as parasites and predators alone have not been capable of terminating budworm outbreaks.

At the present time, the only effective way to reduce budworm defoliation and tree mortality over large areas is the aerial application of chemical insecticides. These do not eradicated the budworm but they reduce populations and keep the trees alive. However, chemical insecticides affect non-target organisms and they may also prolong the duration of outbreaks.

There are several promising alternatives methods to chemical control, but none is available for operational use over large areas. The microbial insecticide Bacillus thuringiensis is the closest to being operationally feasible although addition work is needed to improve its effectiveness.

The spruce budworm is an integral part of out spruce-fir forest ecosystem and in the long run an integrated control approach appears the most promising. This may include the application of chemical insecticides to highly valuable stands, the salvage of damaged stands, the reduction of stands susceptibility to budworm by silvicultural methods and application of other control methods as they become operationally feasible.