Competitive growth of Canada thistle, tall fescue, and crownvetch in the presence of a thistle defoliator, Cassida rubiginosa Müller (Coleoptera: Chrysomelidae)

Published source details Ang B.N., Kok L.T., Holtzman G.I. & Wolf D.D. (1994) Competitive growth of Canada thistle, tall fescue, and crownvetch in the presence of a thistle defoliator, Cassida rubiginosa Müller (Coleoptera: Chrysomelidae). Biological Control, 4, 277-284.
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This study is summarised as evidence for the following.

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	Grow plants that compete with damaging weeds Action Link

Grow plants that compete with damaging weeds

A randomised, replicated trial in fallow farmland in Virginia, USA (Ang et al. 1994) found that sowing plots with tall fescue Festuca arundinacea and crownvetch Coronilla varia at recommended rates reduced shoot weight of the weed creeping thistle Cirsium arvense by 96%, compared to plots with no competitor plants. Sowing competitor plants at half or double the recommended rate reduced thistle shoot weight by 84-85% and 85-86% respectively. Length and weight of thistle roots followed similar patterns. Average thistle shoot weight increased from the first to the second year of competition (6.7 vs. 44.3 g/plot), but decreased after three years of competition (11.5 g/plot). Plots were 2 x 2 m separated by 1 m, in four replicate blocks. Each block had 12 randomised treatments: 0, 0.5, 1 and 2 times the recommended sowing rate (50 and 20 kg/ha of tall fescue and crownvetch respectively) for one, two or three years. The study was part of a biological control experiment using the thistle-eating green tortoise beetle Cassida rubiginosa, which was maintained at a density of >50 adults/m². Numbers quoted were extracted from figures and converted from logarithms.