We have studied the effects of site preparation, hand pulling of Spotted knapweed (Centaurea stoebe), and burning on restoring native plant communities on a knapweed-infested site in western Michigan since 2009. To further isolate experimental plots from knapweed seedfall, all observed knapweed were removed by hand pulling from 231.25-m^2 internal buffers on four 12.5-m × 42.5-m experimental blocks in June and again in July, 2019. The time needed to remove knapweed from buffers during June varied from 1.6 hours for a block with 0.8 kw/m^2 to 6 hours for a block with 4.8 kw/m^2. Removal rates, however, increased with knapweed density (2.0 knapweed/minute at low densities to 3.1 knapweed/minute at high densities). In July, the percent knapweed missed during the first removal in June was greatest at the lowest initial density (17.6%) as compared to the highest density (4.1%). Hand pulling can be an effective control strategy, especially when knapweed densities have been reduced to low levels by mowing, herbicides, burning, or competition from native plants. At low knapweed densities, however, relatively more time is needed to locate individual knapweed, and it is important to apply the treatment at least twice a year prior to seed fall to remove knapweed missed during the first hand pulling application.
Hand Pulling to Control Spotted Knapweed (Centaurea stoebe): Time Requirements and Treatment Strategies
Presenters
Neil MacDonaldGrand Valley State University
Neil MacDonald is a Professor of Biology and Natural Resources Management in the Biology Department at Grand Valley State University in Allendale, Michigan. He received a BS in Natural Resources from the University of Michigan SNR in 1976, a MS in Forestry from Michigan State University in 1983, and a PhD in Forest Soils and Ecology in 1987, also from MSU. Following postdoctoral studies at the University of Michigan SNRE from 1987 to 1994, he accepted a position at GVSU, where he has been on the faculty since 1994. The courses he has taught in the Natural Resources Management Program at GVSU include Introduction to Natural Resources, Resource Measurements and Mapping, Environmental Pollution, Watershed and Wetland Management, Forest Ecosystem Management, Land Reclamation, and the graduate capstone, Perspectives in Biology. His research interests include watershed restoration and management, invasive species control, and restoration of native plant communities on disturbed sites.
