Cheyenne--An Agriculture Department aerial photography survey of 38,000 wildfire-burned acres in Idaho has provided what is believed to be the first evidence that the invasive leafy spurge weed is displacing seedlings of native mountain big sagebrush. Terry Booth, a rangeland specialist with the USDA’s Agricultural Research ServiceRangeland Resources Research Unit in Cheyenne, Wyo., designed the survey using a technique he developed called Very Large Scale Aerial imagery. The survey of Idaho’s “Deep Fire Burn” was done with two cameras at different resolutions aboard a Moyes-Bailey Dragonfly two-seat, light-sport airplane flying just over 300 feet over the area.
When supplemented by ground-based methods, VLSA can be used for early detection of invasive species that might threaten native plant populations. Pesticides and biological-control insects were used to control leafy spurge before and after the wildfire. But the survey, done three years after the fire, showed that leafy spurge still managed to expand in drainage areas and up canyon slopes.