AERIAL DOCUMENTATION OF EFFECTIVE BIOCONTROL OF PURPLE LOOSESTRIFE AT WINCHESTER WASTEWAY, WASHINGTON

摘要

Biocontrol insects (Galerucella sp.) were released at three locations of heavy infestation of purple loosestrife (Lythrum salicarid) along the Winchester Wasteway in central Washington beginning in 1995. 1:5000 scale natural color aerial photography during the flowering and autumn leaf seasons in 1995, 1998, and 1999 has documented at 1-m resolution the expansion of insect-impacted loosestrife areas, now extending for distances measurable in kilometers. Biocontrol damage between the latter dates spread at about 1.4 km/yr at a site with numerous ponds and at about 2.3 km/yr along a stream environment. This study also revealed the expansion of the common reed (Phragmites australis), even against healthy loosestrife, as the next threat to the habitat and water flow through the wasteway.