• Ashley, Marshall D.
  University of Maine
  
• Rea, James
  University of Maine
  
• Wright, Linda
  University of Maine
  

The spruce budworm (Choristoneura fumiferana, Clem.) infestation is continuing at epidemic levels throughout northeastern North America's spruce-fir forest. This article describes research to identify at what minimum scale aerial photography can be used to assess budworm damage. Color and color infrared imagery taken at several times of the year and interpreted using several viewing methods have been evaluated to find if new infestations, tree mortality and stands requiring spraying to prevent excessive future mortality can be identified.

Color photography obtained in the summer at the height of budworm clipped needle browning was best for interpreting current moderate or heavier feeding. Early summer or fall photos taken when the currently fed needles weren't on the trees were most suitable for evaluating past feeding and overall tree condition. Mortality was best identified on color infrared early summer or fall imagery.

Scale and viewing method greatly influenced interpretation accuracy. Individual tree detail could be observed at scales of 825 ft./in/ and larger. Tree and stand condition were most accurately interpreted using a 7X monocular viewer on the backlighted and outside of the frame. Mortality counts were equally well made using two, four or seven power stereoscopic and seven power monoscopic viewing at scales of 2640 ft./in. and larger.