Cyrtobagous Salviniae: Solution to Invasive Weed

The introduction of the Brazilian insect ‘Cyrtobagous salviniae’ provided an effective and cost-efficient solution to the invasive aquatic weed ‘Salvinia molesta’ in Madhya Pradesh.

Background

• Infestation by Salvinia molesta: A Village in Betul district, Madhya Pradesh, faced severe livelihood challenges due to the infestation of the aquatic weed Salvinia molesta, locally known as “Chinese Jhalar.”
• Timeline of Infestation
  • The infestation of Salvinia molesta began in 2018.
  • By 2022, the reservoir was overwhelmed, leading to significant issues.

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Salvinia molesta

• About: It is a dense invasive free-floating plant that does not attach to the soil, but instead remains buoyant on the surface of a body of water. 
  • It has become a significant problem in various regions due to its rapid growth and ability to form dense mats on water surfaces.
• Origin and Spread
  • Salvinia molesta is originally from Brazil and Argentina.
  • It has spread worldwide through the aquarium and horticulture industries, reaching Australia, Africa, Madagascar, India, Sri Lanka, Southeast Asia, the Philippines, Indonesia, Papua New Guinea, Fiji, and New Zealand.

• Introduction to India
  • In India, the weed was first observed in Veli Lake, Thiruvananthapuram, in 1955.
  • By 1964, it was classified as a ‘pest’ in India.
• Ecological Impact
  • Salvinia molesta has a significant ability to choke rivers, canals, lagoons, and other water sources, causing severe ecological disruptions.
  • It outgrows and replaces native aquatic plants, affecting food sources and habitats for animals and waterfowl.
• IUCN List: The IUCN (International Union for Conservation of Nature) has added Giant Salvinia to its list of the world’s worst invasive alien species.Impact of the Invasion of Salvinia Molesta
• Ecological and Economic Damage
  • The weed’s dense coverage made water extraction impossible.
  • Fish populations died, and lotus plants rotted due to the infestation.
• Impact on Local Livelihoods
  • The severe weed growth disrupted local fishermen’s livelihoods.
  • Many fishermen were forced to migrate for work due to the economic hardship caused by the infestation.

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Introduction of Cyrtobagous Salviniae as a Solution

• About Cyrtobagous salviniae: It is used as an agent of biological pest control against the noxious aquatic plant giant salvinia (Salvinia molesta).
  • ‘Cyrtobagous salviniae’ was introduced to India from Australia in 1982, with successful trials in Bangalore and Kerala before reaching Central India.
• Proposed Solution
  • A team from Jabalpur proposed using the Brazilian insect ‘Cyrtobagous salviniae’, which targets and feeds on Salvinia molesta to control its spread.
  • These insects are bred at the Weed Research Directorate in Jabalpur, where research is also conducted to study their effects.
• Implementation
  • The insect was introduced to the affected ponds in September 2022.
  • Regular releases of the insect continued until March 2023.
• Results
  • The program achieved significant success, with the weed completely decomposing within 18 months, ahead of the expected time frame.
  • The effectiveness of the program led to crystal-clear water in previously affected lakes.
• Sustaining Cyrtobagous salviniae with Host Plants
• • As the presence of Salvinia molesta diminishes, additional green weed is introduced to sustain the insect population.
  • 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

Advantages of the Organic Solution

• Cost Effective: The use of ‘Cyrtobagous salviniae’ was significantly more cost-effective compared to manual removal methods, which were estimated to cost 15-20 crores and take 5-6 years.
• Minimised risks: The organic method not only solved the problem efficiently but also minimised risks associated with manual removal of weeds.

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