Weevil Wonder
Journal of Aquatic Plant Management 44: 115-121 (2006)
Giant salvinia (Salvinia molesta) is a noxious aquatic fern native to Southern Brazil that has threatened many freshwater ecosystems. Giant salvinia reproduces rapidly by fragmenting part of their stems to create a new plant. Its overgrowing has replaced native vegetation, altering the food web of the aquatic ecosystems, and also reduced dissolved oxygen levels, which eventually asphyxiates all aquatic life. It hinders irrigation, clogs waterways and promotes diseases in the stagnant waters the fern creates.
Daniel Flores and J.W. Carlson of the USDA introduced the salvinia weevil (Cyrtobagous salviniae) to control the fern. Herbicides usually exacerbate the situation or are not effective. The places where the researchers introduced the weevils have a significant decrease of the fern and an increase in dissolved oxygen levels. The giant salvinia population has remained constant and the weevils have shown to only consume the fern and nothing else. The authors say more research is needed, but biocontrol has shown to be an effective option.
February 6th, 2010 at 4:30 pm
The fact that the salvinia weevil only consume giant salvinia ferns is intriguing. This feeding behavior definitely deems the weevil to be a potent method of control for this plant because the presence of other plants will not deter from this biocontrol strategy. I do wonder how the giant salvinia can take over the aquatic environments it invades if this weevil is fixed on consuming it. Perhaps this is due to the weevil not eating the giant salvinia at a rate faster than it grows, or maybe the weevils are not found where this fern grows. If the first possibility is true, then researchers should consider introducing more salvinia weevils into ecosystems where this plant grows or using other methods of control in conjunction to restrain the giant salvinia. On the other hand, if the second point holds, then scientists should develop methods to import weevils into the giant salvinia’s environments without harming the insects by this change in natural habitat.
February 8th, 2010 at 1:22 am
This seems like a very interesting article. It appears that weevils are very useful in biocontrol. I’m curious as to what qualities they have that gives them the ability to control certain plant growth so successfully. Also, do the weevils have any effect of their own on the dissolved oxygen levels? Do they breathe oxygen? Or is it just that they reduce the amount of the fern. Also, does anything consume weevils? This could also affect the ecosystem.