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Individual study: Herbivory and novel weapons: no evidence for enhanced competitive ability or allelopathy induction of Centaurea diffusa by biological controls

Published source details

Norton A.P., Blair A.C., Hardin J.G., Nissen S.J. & Brunk G.R. (2008) Herbivory and novel weapons: no evidence for enhanced competitive ability or allelopathy induction of Centaurea diffusa by biological controls. Biological Invasions, 10, 79-88


This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.

Grow plants that compete with damaging weeds Natural Pest Control

A randomised, replicated, controlled trial in 2005 in a greenhouse in Colorado, USA (Norton et al. 2008) found reduced growth of diffuse knapweed Centaurea diffusa (an invasive weed) when grown in competition with prairie sagewort Artemisia frigida (diffuse knapweed weight of 1.5 g/plant) or blue grama grass Bouteloua gracilis (0.5 g/plant), compared to growing diffuse knapweed alone (2.2 g/plant). Diffuse knapweed also reduced yield of prairie sagewort by 58% and of blue grama by 35% compared to growing either species alone. The experiment used 2 litre pots with one diffuse knapweed plant and two prairie sagewort or blue grama plants, and controls with each species individually. Pots containing diffuse knapweed also received one of four different treatments with herbivorous insects used for biological control. Each treatment was replicated 12 times.