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.

Organic Farming - Methods

"An organic farm, properly speaking, is not one that uses certain methods and substances and avoids others; it is a farm whose structure is formed in imitation of the structure of a natural system that has the integrity, the independence and the benign dependence of an organism"
Wendell Berry "The Gift of Good Land"


Organic farming is a production system which favors maximum use of organic material and discourage use of synthetically produced agro-inputs, for maintaining soil productivity and fertility and pest management under conditions of sustainable natural resources and healthy environment.

Soil Management

Plants rely primarily on soil for water and nutrients. It is therefore soil health is utmost important for organic farmers. But providing adequate nutrients is often a challenge.

Crop rotation, green manure, intercropping, cover cropping, mulching etc., help to provide nutrient to the soil, as well as increasing the soil’s organic matter. Certain processed fertilizers such as seed meals, compost, bloodmeal, animal excreta, naturally-occurred-fertilizer, eg. rock phosphate and limestone are used. Altogether these methods help to control erosion, promote biodiversity, and enhance the health of the soil.

Weed Control

Weed control is the botanical component of pest control, stopping weeds from reaching a mature stage of growth when they could be harmful to domesticated plants and livestock.

Typically, a combination of methods is used in organic farming. The most basic is manual weeding, with hand or aided with some simple tools. Flaming, a traditional technique is sometime used, but subjected to local legislation. Mechanically tilling and ploughing, are effective ways to control weeds, were however involve diesel-powered tractor, unfortunately which is not an environmental-friendly machine. Other techniques for controlling weeds include mulch, solarization, crop rotation, drip-irrigation ( limit weeds access to water ) natural pre-emergence herbicide ( e.g. corn gluten meal, garlic, clove oil, borax, pelargonic acid, table salt, vinegar, and various other homemade remedies).

Control Other Organisms

Organisms aside from weeds which cause problems include athropods (e.g. insects, mites) and nematodes. Fungi and bacteria can cause disease.
Insect pests are a common problem, and insecticides, both non-organic and organic, are controversial due to their environmental and health effects. One way to manage insects is to ignore them and focus on plant health, since plants can survive the loss of about a third of lead area before suffering severe growth consequences.

To avoid using insecticides, one can select naturally-resistant plants, put bags around the plants, remove dying material such as leaves, fruit, and diseased plants, covering plants with a solid barrier ("row cover"), hosing, encouraging and releasing beneficial organisms and beneficial insects, planting companion plants and polycultures, various traps, sticky cards and season extension. Biological pest control uses natural predators to control pests. Recommended beneficial insects include minute pirate bugs, big-eyed bugs, ladybugs, lacewings, parasitoid wasps, praying mantis and predatory mites.

Several of pesticides approved for organic use have been called green pesticides such as spinosad and neem. Generally, but not necessarily, organic pesticides are safer and more environmentally friendly than synthetic pesticides. The main three organic insecticides used are Bt (a bacterial toxin), pyrethrum and rotenone. Nicotine sulfate may also be used; although it breaks down quickly, it is extremely toxic, nearly as toxic as aldicarb. Less toxic but still effective organic insecticides include neem, spinosad, soaps, garlic, citrus oil, capsaicin (repellent), Bacillus popillae, Beauvaria bassiana, and boric acid. Pesticides should be rotated to minimize pest resistance.

The first disease control strategy involves keeping the area clean by removing diseased and dying plants and ensure that the plants are healthy by maintaining water and fertilization. Polycultures reduce the ability of disease to spread. Disease-resistant cultivars can be purchased. Organic fungicide include the bacteria Bacillus subtilis, Bacillus pumilus, and Trichoderma harzianum which are mainly effective for diseases affecting roots. Bordeaux mix, sulfur, lime sulfur, potassium and sodium bicarbonate can be used as an organic fungicide in various forms