Thursday, August 1, 2013

Salvinia minima - Common Salvinia

Salvinia minima is a species of aquatic, floating fern of Salviniaceae family native to South America. 

The leaves of S. minima are small and oval, ranging from 0.4 to 2.0 cm in length.  The leaves grow in sets of three, with two leaves floating on the surface and one leaf dissected, hanging underneath.  Fine white hair grow uniformly on the leaf surface.  Brown hairs present on the underside of leaves.  S. minima is rootless.
Salvinia minima is classified as an invasive species on the Global Invasive Species Database.  It can be a nuisance to recreational watercraft, have adverse affects on fish farming, rice farming, and poses a serious threat to native species and biodiversity.
Salvinia minima grows on the surface of still freshwater.  Although it is sterile, S. minima can reproduce quickly very quickly asexually through fragmentation.  Buds and rhizome fragments can also remain dormant for long period of time when growth is less favorable.

S. minima undergoes 3 stages of growth.  In the primary stage, the leaves will lie flat on the water surface.  In the secondary stage, the leaves multiply and curl upward.  In the tertiary stage, the leaves become more dense and almost vertical due of crowding.

S. minima can easily out-compete and inhibit the growth of native water plants.  Mats of S. minima can block sunlight from entering the water.  S. minima, which has no nutritional value, is not favoured by fish or bird species as a food source.

In order to protect native ecosystems, numerous effort have been taken to control or eradicate the growth of Salvinia minima.   Herbicides that have been used with best success include : fluridone, imazamoz, and penoxsulam.  Successful biological control agent includes Crytobagous salviniae,  the salvinia weevil native to South America ; and Samea multiplicalis, the salvinia stem-borer moth native to southern US.

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