Eichhornia crassipes = Biological Control Insects

Eichhornia crassipes = Biological Control Insects

Biological Control of Invasive Plants: Water hyacinth (Eichhornia crassipes)

 

Water hyacinth was introduced from South America into the US in 1884. Since then it has spread into many lakes and rivers of the southern US, making it one of the most troublesome aquatic plants in the country.

The first biocontrol insect released against water hyacinth in US was the mottled water hyacinth weevil (Neochetina eichhorniae). Its life cycle is 90 to 120 days, depending on temperature and other factors; both the adults and the larvae feed on various parts of the plant. This weevil was first released in Florida in 1972, and subsequently in several other states. It also has been established in Australia, Fiji, Honduras, India, Malaysia, Papua New Guinea, South Africa, Thailand and has been released in several other countries.

The second biocontrol insect released against water hyacinth in the US was another Neochetina species: the chevroned water hyacinth weevil (Neochetina bruchi), first released in Florida in 1974. Its life cycle is shorter than that of N. eichhorniae; its impact is similar.

Another biological control insect introduced against water hyacinth is the Argentine water hyacinth moth (Sameodes albiguttalis). Its life cycle is only 30 days; the larvae are the only life state that feeds on the plant. It was released and is established in Florida, Louisiana and Mississippi, as well as in Australia, South Africa and Sudan. It may retard growth in the early stages of water hyacinth mat development.

Not all biocontrol insects are from somewhere else. The larval stage of Bellura densa (formerly Arzama densa), a native southern US moth commonly known as pickerelweed borer, also attacks water hyacinth. Efforts were made in the early 1980s to augment natural populations of the moth's larvae in an effort to cause an impact on water hyacinth plants in Louisiana. There was little impact.

  • Bellura densa Native moth, adult on water hyacinth leaf
  • Bellura densa Native moth, larva in pickerelweed stem
  • Bellura densa Native moth, Neochetina eichhorniae larva on left; Arzama densa larva on right
  • Bellura densa Native moth, Telenomus parasite on Arzama densa eggs