Treatment of Crassula helmsii - a case study

Published source details Child L.E. & Spencer-Jones D. (1995) Treatment of Crassula helmsii - a case study. Plant Invasions: General Aspects and Special Problems, Kostelec nad cernymi lesy, Czech Republic, 195-202.
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This study is summarised as evidence for the following.

	Action	Category
	Crassula helmsii: Chemical control using herbicides Action Link

Crassula helmsii: Chemical control using herbicides

A small, controlled, before-and-after trial in 1992 in two lakes in West Sussex, UK (Child & Spencer-Jones 1995) found that spraying C. helmsii with glyphosate reduced plant height and cover, but dichlobenil and diquat had no effect (although no statistical tests were carried out). C. helmsii cover decreased from 100% to 60% 11 days after spraying emergent plants with glyphosate, but did not change in the control plot. Thirty five days after spraying, treated plants were shorter (4 cm) than control plants (15 cm). At the same lake, a small plot of submerged C. helmsii was treated with dichlobenil but this had no effect (no data provided). At the second lake, diquat alginate did not affect cover of submerged C. helmsii (before: 100%; 35 days after: 95%). In a second trial at the same site, diquat did not affect cover of submerged (before: 95%; 16 days after: 95%), floating (before: 70%; after: 70%) or emergent plants (before: 15-20%; after: 15%). Glyphosate with an active ingredient concentration of 2.5 kg/ha was sprayed onto leaves at three 1 x 6 m plots in August. One control plot was left untreated. Dichlobenil granules were applied at 150 kg/ha at a 1 x 4 m plot in July. Diquat alginate, containing 100 g/l active ingredient, was applied at 10 l/ha to the water surface in August. Diquat, containing 200 g/l active ingredient, was applied at 25 l/ha to shallow areas and 50 l/ha to deep areas in September. Sites were monitored twice before (June-July) and three times after (August-October) treatments.