How a Brazilian insect helped clean Madhya Pradesh ponds | Cyrtobagous salviniae

After five long years of disappointment, Raju Daire is hopeful that the crisis clouds looming over his livelihood have finally cleared. Raju, a member of the fishermen's community, lives in Machhli Kanta Basti near Sarani Reservoir in Betul district, Madhya Pradesh. Around 250 families like his reside in this colony, all of whom rely on the fish obtained from the reservoir for their livelihoods.

The last five years have been nothing short of a disaster for these fishermen. The disaster was caused by a highly invasive foreign aquatic weed, known to scientists as Salvinia molesta and to local residents as "Chinese Jhalar." The situation in the reservoir has improved compared to what it was before, and the reason behind this change is quite remarkable.

The infestation began in 2018, and by 2022, the reservoir was so overrun with the weed that it severely affected the community's ability to sustain their livelihoods. There was no employment, and many people had to migrate for work. The weed grew so thick that people could have walked on it.

During this period, drawing water became impossible, all the fish died, and the once-beautiful lotus plants rotted. This weed, originally from Brazil and Argentina, is believed to have spread worldwide through the aquarium and horticulture industries. It has now taken root in Australia, Africa, Madagascar, India, Sri Lanka, Southeast Asia, the Philippines, Indonesia, Papua New Guinea, Fiji, and New Zealand.

In India, the weed was first observed in Veli Lake in Thiruvananthapuram in 1955, and by 1964 it had been classified as a pest. Its ability to choke rivers, canals, lagoons, and other water sources is tremendous.

After much hardship, the community learned about a team from Jabalpur who informed them that the "Chinese Jhalar" in their pond could be removed if they were willing to collaborate. The team introduced them to a solution involving an insect. Together, they distributed these insects across the pond, with the team advising that it would take 12-18 months for the problem to be resolved. Remarkably, the issue was solved even before the expected time.

The insect, known as Cyrtobagous salviniae, proved to be highly effective. The Sarani Thermal Power Station, located in Betul district, has a lake covering an area of around 2,800 acres. By 2020, the entire pond was filled with the Salvinia weed, raising serious concerns among the authorities.

In 2022, when we started this programme, we began in September, and by March 2023, we had introduced the insects into the pond. Every time we visited the area, we released more insects. Now, in all the places where we implemented this programme, such as Gadchiroli, Chandrapur, and others, the lakes have crystal-clear water. In every location where the programme was initiated, we achieved 100% success.

The pond, which was entirely filled with Salvinia molesta in 2020, saw the weed completely decomposed within a year and a half after the insects were introduced. These insects are bred at the Weed Research Directorate in Jabalpur, where research is also conducted to study their effects.

As the weed presence diminishes, more of the green weed is introduced so that the insects can continue to thrive. These insects rely on the weed as their host, and if the weed is not present, the insects cannot survive. The green weed is cultivated in tankers, where it is grown and later introduced into the pond.

As you can see, this area was once overgrown, but now the entire section is decayed. The growth point has been eradicated, and it will no longer grow.

Sir, we heard that there was an alternative plan to remove the weed manually, but it was very expensive. It would have cost 15-20 crores and taken 5-6 years. The process was also risky, difficult to evaluate, and would have required much more time. We were not confident that the weed would be completely eradicated. However, this organic solution has proven to be effective, and the problem is unlikely to recur.

These insects were brought to India from Australia in 1982. The first successful trial was conducted in Bangalore, followed by Kerala. The first trial in Central India was carried out in Padua village in Katni district. Scientists have suggested this insect as a solution to control the invasive weed, successfully trying it in Gadchiroli and Chandrapur in Maharashtra.