Water Hyacinth Cultivation Methods and Key Technical Points Explained
The official name of water hyacinth: Eichhornia crassipes, also called water lettuce. The stems and leaves of water hyacinth hang suspended above the water, and its tillering branches creep along the water surface. The flowers are multi-angled and trumpet-shaped, with brilliant and beautiful colors. The leaves are emerald green with a darker tone. The leaf margins are entire, smooth and textured. The fibrous roots are well developed, and tillering propagation is fast; management is extensive, making it a good plant for beautifying the environment and purifying water quality. In areas suitable for its growth, it often takes over the water surface due to over-reproduction, affecting shipping, suffocating fish, and harming health; it is difficult to destroy and hard to eradicate at the root. It is a kind of organism with two sides, and should not be planted on a large scale.
Harm
1. It blocks navigation channels, affects shipping and drainage, and becomes the number one enemy of agriculture, water conservancy, and environmental protection;
2. It restricts the flow of water bodies; without sunlight reaching the water, the water becomes foul-smelling, the dissolved oxygen content in the water decreases, the growth of plankton is inhibited, and the ecological environment of rivers and streams is destroyed.
3. It provides breeding grounds for schistosomiasis and pathogens such as encephalitis and influenza, breeds mosquitoes and flies, and provides opportunities for mosquito larvae to breathe and reproduce.
4. It destroys drinking water resources. Because it causes blockage, water bodies cannot flow freely, and various pollution sources such as heavy metal elements and other trace elements harmful to human health cannot be effectively removed, so people directly or indirectly take in contaminated water sources.
5. Water lettuce covering the water surface also increases water evaporation, which is 8 to 10 times higher than that of an open water surface, causing water source loss.
6. Impact on freshwater quality at water source collection points. A large amount of water lettuce covering the water surface will lower the pH value of the water; increase CO2 concentration; increase the odor value concentration and colority of the water; and also increase the acidity in the water, greatly reducing the use value of the water resource until it is no longer drinkable.
Control
Chemical control
After a period of effort, scientists have already achieved certain results in chemical control. A comparative study of the control effects of four herbicides (paraquat, glyphosate, bensulfuron-methyl, and oxadiazon) on water hyacinth showed that paraquat had the most significant effect, followed by glyphosate; bensulfuron-methyl and oxadiazon both had a certain inhibitory effect, but could not achieve a lethal effect. In addition, paraquat has a certain lethal effect on the adult water hyacinth weevil, a natural enemy that feeds exclusively on water hyacinth, while glyphosate has no direct effect on its adults, eggs, or larvae. 41% BIOPORCE aqueous solution controls water hyacinth rapidly, with good efficacy, and also has a longer residual effect, with no observed adverse effects on aquatic animals.
Biological control
Biological control of water hyacinth began in the early 1960s with investigations of natural enemies in Uruguay, South America, the place of origin of water hyacinth (Silveira-Guido, 1971). In 1967, the Commonwealth Institute of Biological Control began investigation and research in northern South America and the West Indies, and in 1968 the United States Department of Agriculture also began biological control research on water hyacinth in a laboratory in Argentina. In 1978, Australia conducted this research in Brazil and neighboring countries. In Uruguay, Trinidad, Argentina, Florida in the United States, as well as other South American countries and India, more than 70 species of arthropods that feed on water hyacinth were found, and in Brazil 3 species of arthropods that feed on water hyacinth were also found, as well as 3 species of mites Amblyseius glorius, A. pederosus (EL-Banhawy, 1979) and Flechtmanniaei chhorniae. In addition, there are also reports of two species of invertebrates that feed on and damage water hyacinth, as well as manatees, grass carp, and fungi. In the process of selecting natural enemies, insects and mites have been given special attention because of their small size and ease of rearing and study. At present, the organism most used in biological control is the water hyacinth weevil. In the long process of natural evolution, organisms and organisms restrict and coordinate with each other, limiting their respective populations to a certain range, maintaining a certain number, and forming a stable ecological balance system. Under the slogan of "raise on a large scale and specially," water hyacinth was once promoted in many places in southern China as a high-yield aquatic feed. Beginning in the 1980s, water hyacinth began to overrun many river channels in southern China. After breaking away from the control of natural enemies in its place of origin, water hyacinth reproduced wildly, destroying the balance among local species and causing the death of large numbers of aquatic animals and plants. But the lesson brought by the introduction of water hyacinth forces us to treat the introduction of exotic species with caution. Therefore, up to now, the weevil still remains in the laboratories of Chinese scientists. Safety experiments on the water hyacinth weevil and experiments on controlling water hyacinth show that it has very strong specificity to water hyacinth and also has a clear control effect on the growth of water hyacinth.
In the strategy of integrated management, water hyacinth can be retained on one side of the river channel to preserve the weevil population, while spraying herbicide on the other side can achieve the effect of integrated management. Directly spraying the herbicide Roundup on water hyacinth with weevils can both effectively control the growth of water hyacinth and retain a certain population of weevils, but the amount of Roundup used must be appropriate. Choosing a dosage that can effectively inhibit the growth of water hyacinth plants and population reproduction while making it difficult to kill the plants in the short term is the key to maintaining the existence of the weevil population. Using this method, as long as 1/10 of the normal dosage of Roundup preparation is used, a very significant control effect can be obtained. This will largely avoid the environmental and cost problems caused by excessive use of Roundup.
Control using river crabs
When the water temperature reaches 15 °C in April to May, water hyacinth will begin to reproduce. At this time, taking advantage of the river crab's preference for feeding on the new roots and new stems of water hyacinth, releasing a certain amount of juvenile crabs or megalopae into ponds with more water hyacinth can effectively control the growth of water hyacinth and also increase crab yield and survival rate.
Manual salvage
Manual salvage is a primitive method, but it is very effective. The key is determining the salvage time; salvaging before water hyacinth begins to reproduce, or after pesticide application has taken effect, can achieve twice the result with half the effort. In particular, combining manual salvage with chemical control, when herbicides cause the water hyacinth to wither and then salvaging it, the effect is very obvious.