Managing Weeds Naturally: Know how scientists controlled Salvinia molesta attack in Satpura reservoir

Managing Weeds Naturally: During the year 2019-20, the 2900 acre reservoir at Satpura Thermal Power Station was completely affected by Salvinia molesta. This infection posed a serious threat not only to the ecological balance of the reservoir but also to the economy there.

Aquatic Weeds Salvinia molesta, commonly known as water fern, has become a problem for India. Especially in weed management. Known to grow fast and form dense mats, Salvinia molesta has severely damaged water bodies. It works to prevent their ecological balance. An example of the impact of this invasive species is the reservoir of Satpura Thermal Power Station (STPS) in Sarni, Madhya Pradesh.

Crisis at Satpura Reservoir

During the year 2019-20, the 2900 acre reservoir at Satpura Thermal Power Station was completely affected by Salvinia molesta. This infection posed a serious threat not only to the ecological balance of the reservoir but also to the economy there. It especially affected the livelihood of the fishermen. These fishermen depend on this for their income. The dense weed cover made fishing very difficult. Due to this, the number of fish started declining.

Given the seriousness of the situation, there was an immediate need to work on natural weed management. Preparations were made to control aquatic weeds with the help of traditional methods of removing aquatic weeds, such as with the help of machines and with the help of chemicals. However, there was a possibility of large-scale water contamination and environmental damage. A sustainable and useful solution for natural weed management was needed.

Role of ICAR-Directorate of Weed Research

In response to the crisis caused by Salvinia molesta, ICAR-Directorate of Weed Research, Jabalpur approached to develop a proactive solution for natural weed management. The consulting project funded by Madhya Pradesh Power Generation Company Limited was started in June 2022. Its objective was to prevent the spread of Salvinia molesta. Along with this, the ecological balance of the reservoir is also to be restored and the social and economic impacts on the fishermen there are also being minimized.

The Directorate proposed a Biological Control Strategies. In which the insect Cyrtobagus salvinia was used as a bioagent. Cyrtobagus salvinia is a weevil known for its potency in controlling Salvinia molesta populations. Adult weevils eat the growing plants of the weed. While their larvae, or grubs, penetrate the rhizosome, causing great damage to it and eliminating the weed, which emerged as the most important for natural weed management.

How do biological control strategies work in natural weed management?

This project for natural weed management was launched in October 2022, in which Cyrtobagus salvinia bio agents were released at the rate of 22,500 per hectare. Its initial release was strategically timed to coincide with the onset of the winter season. This is usually the period of low weed growth, allowing the bioagents to establish themselves more effectively.

To ensure even spread of the bioagent throughout the reservoir, 3-4 boosts were done at monthly intervals after the initial release. These boosts were crucial to maintain adequate bioagent population to repeatedly put pressure on the Salvinia molesta population, which is naturally used for weed management. Over time, the weevil spread throughout the reservoir, gradually reducing the weed cover.

The impact of this biological control strategy was closely monitored by ICAR-Directorate of Weed Research. Monitoring indicated that within 18 months, Salvinia molesta infestation was effectively controlled, leading to complete elimination of the weed in the reservoir. This success was not only a testament to the success of Cyrtobagus salviniae as a bioagent, but also a testimony to the planning and execution of the project properly.

Natural weed management and socio-economic benefits for local communities

Successful control of Salvinia molesta has brought profound socio-economic benefits to local fishermen. The reduction in weed cover has led to improved fish populations in the reservoir, which in turn has led to increased catches and improved incomes for fishermen. This result highlights the socio-economic importance of biological control in aquatic ecosystem management. 

The success of the natural weed management project also demonstrated the potential of biological control as a sustainable alternative to more conventional methods. As compared to the estimated cost of Rs. 15.0 crore over five years for mechanical removal of weeds from the reservoir, the biological control strategy implemented by the Directorate was highly cost effective with a total expenditure of only Rs. 49 lakhs. Moreover, the biological method was not only less expensive but also more time saving, environment friendly and sustainable in the long run.

Recognition and Promotion of Technology

In recognition of the successful elimination of Salvinia molesta from Satpura reservoir, the officials of Satpura Thermal Power Station organized a function on 3rd July, 2024. The scientists who carried out natural weed management were felicitated at the event. ICAR-Directorate of Weed Research, Jabalpur appreciated the excellent work of the scientists and their contribution in cleaning the reservoir and improving the livelihood of the local fishing community.

Success of biological control strategies

The success of this biological control strategy has led to its use in other areas facing similar challenges with Salvinia molesta. The technique has worked successfully in several other water bodies in Maharashtra, Chhattisgarh and Madhya Pradesh. In Maharashtra, the technique was applied in Ghodapet (110 acres), Junona Lake (750 acres), Erai Dam (250 acres) in Chandrapur district and Lanjad pond (40 acres), Hatti lake (150 acres) in Gadchiroli district for natural weed management. In Chhattisgarh, the technique was applied in Talpuri lake (80 acres) in Durg district. Madhya Pradesh, was used in Padua village pond (50 acres) in Katni district.

Successful use at different locations for weed management

The successful use at different locations for natural weed management has shown the excellent work and effectiveness of biological control strategies in different ecological and geographical contexts. Widespread adoption of this technology is a major step towards managing aquatic weeds in India, ensuring sustainability of water resources and protecting the livelihoods of people dependent on these ecosystems.

Natural weed management and biological control

Natural weed management and biological control of Salvinia molesta in the Satpura reservoir at Sarni in Madhya Pradesh is a great example of how science and technology can be used to address environmental challenges as well as improve socio-economic conditions.

Frequently Asked Questions in Natural Weed Management

Q1: What is natural weed management?

Answer: Natural weed management is a strategy that involves growing or promoting beneficial vegetation while suppressing unwanted plants.

Question 2: How to get rid of the aquatic weed Salvinia molesta

Answer: The insect Cyrtobagus salviniae is used as a bioagent. Cyrtobagus salviniae is a weevil that controls Salvinia molesta populations. Adult weevils eat the growing plants of the weed. While their larvae, or grubs, burrow into the rhizosome, causing severe damage that kills the weed, which has emerged as the most important natural weed management method.

Question 3: How to do organic weed management?

Answer: Delayed seeding can be an effective method of weed control, providing an alternative to tillage before seeding or after harvesting. Tillage should begin early in an effort to warm the soil and encourage weed growth.

Question 4: How is aquatic weed management done?

Answer: Aquatic weed management is a method of controlling invasive aquatic plants in aquatic ecosystems. There are many methods used to control these plants. Some of these methods are-

Prevention: Cleaning and maintenance of ponds

Biological methods: Using biological methods like grass carp.

Mechanical methods: Cutting, netting, and raking.

Chemical methods: Using aquatic herbicides.

Dredging and chaining: Removing weeds along with roots and rhizomes by mechanical force.

Creating containment for floating debris.

Question 5: Which is the most dangerous aquatic weed?

Answer: Eichhornia crassipes is the most problematic aquatic weed in the world. It is also called the Terror of Bengal. Due to its very high rate of growth, it can cover the surface of entire water bodies, obstructing or blocking them and affecting other aquatic life.