• Church Jr., Thomas W.
  

Defoliation by insect pests has often resulted in heavy mortality in the forests of North America. Among the more notable offenders and their coniferous hosts are the spruce budworm on spruce and balsam fir, the pine butterfly on ponderosa pine, the gypsy moth on white pine, the hemlock looper on hemlock, the tussock moth on Douglas fir, and the larch sawfly on tamarack, Under favorable conditions these insects can build up to epidemic proportions and sweep disastrously through millions of acre of valuable timber, Defoliated by forest fires and needle cast fungi also cause mortality in conifers.