Successful management of Ludwigia grandiflora
Ludwigia grandiflora (Onagraceae: EPPO A2 List) is native to South and Central America and Southern parts of the USA. In Europe L. grandiflora is one of 14 species included in the list of invasive alien species of Union concern. In Germany, the species is listed on the German Black List – Action List where rapid eradication of infestations is recommended and the first population was found in a lake isolated from the River Leda by an embankment in Lower Saxony region (North-western Germany) in 2004. In 2011, a study on seed production and viability was conducted by collecting and measuring seed capsules from the lake and germinating seeds on damp tissue in Petri dishes. Seed production was significantly correlated with capsule length and viability was recorded at 45 %. However, during the field work no evidence of seed germination was discovered and plant material was the offspring of the previous years’ shoots. Hand weeding was evaluated as a management practice for L. grandiflora at five sites of varying size (1.5 m – 30 m2) within the lake where varying densities were removed between June and October. Hand weeding was shown to be effective and at one site where the highest biomass per m2 was harvested, total eradication was achieved after just one application. However, at sites where L. grandiflora was mixed with native species hand pulling was less successful. In 2013, in three days more than 99 % of the biomass (25 tonnes of fresh mass) of L. grandiflora was removed from the lake with follow up measures to remove plant regrown in the same year (one day removal), and in 2014 (two one day removal treatments), and 2015 (one day treatment). From 2013 to 2015, L. grandiflora was eradicated in more than 99 % of the lake with 232 man-hours invested. The cost to remove the plant biomass and have it incinerated was 980 EUR.
Sources
Hussner A, Windhaus M, Starfinger U (2016) From weed biology to successful control: an example of successful management of Ludwigia grandiflora in Germany. Weed Research, DOI: 10.1111/wre.12224.