EFFECTS OF VISION® APPLICATION ON MOOSE WINTER BROWSING AND HARDWOOD VEGETATION

Abstract

Two years after aerial spraying with Vision® (glyphosate) at 0.80, 1.06, and 1.60 kg acid equivalents (a.e.)/ha, we found live hardwood stem densities on 7 mixedwood clear-cuts reduced by 48, 65, and 61%, while those on controls had increased 19%. Winter browsing by moose (Alces alces) decreased both 6 and 18 months after spraying on all treatment units, including controls, but was consistently lower on sprayed areas. The two highest application rates resulted in the lowest browsing levels. Conversely, winter track data showed no differences in use among sprayed areas and controls, nor any differences among treatments. This finding suggested that moose still travelled through sprayed areas, but did not stop as frequently or as long to browse, or else that they browsed more early in winter before we began tracking. Since 0.80 kg a.e./ha controlled hardwood and herbaceous competition as well and 1.06 and 1.60 kg a.e./ha, and also showed signs of increased moose use two years post-spray, (while the two higher rates did not), we recommend that where spray programs are concentrated in one management unit, application at 0.80 kg a.e./ha would be best for moose. However, the low browsing intensities found in this study suggested that moose densities were low enough that food would not be a limiting factor. Thus, the small percentage of forests currently treated with Vision® in Ontario would not be expected to affect moose populations.