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ARS Home » Southeast Area » Fort Lauderdale, Florida » Invasive Plant Research Laboratory » Research » Publications at this Location » Publication #188336
Title: THE DECLINE OF WATER HYACINTH ON LAKE VICTORIA WAS DUE TO BIOLOGICAL CONTROL BY NEOCHETINA SPP.

Author
item WILSON, J - U. OF STLLENBOSHCH, SA
item Center, Ted
item HILL, MARTIN - GRAHAMSTOWN UNIV. S. AFRI
item JULIEN, M - CSIRO
item KATAGIRA, F - PLANT HEALT SVS, TANZANIA
item HJOKA, S - KENYA AG. RES INSTITUTE
item OGWANG, J - NAT'L AG RES ORG, UGANDA
item REEDER, R - CABI-BIOSCIENCE
item Van, Thai

Submitted to: Aquatic Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/19/2006
Publication Date: 6/1/2007
Citation: Wilson, J.R., Center, T.D., Hill, M., Julien, M.H., Katagira, F.F., Hjoka, S.W., Ogwang, J., Reeder, R.H., Van, T.K. 2007. The decline of water hyacinth on Lake Victoria was due to biological control by Neochetina spp. Aquatic Botany. 87:90-93.

Interpretive Summary: A massive infestation of waterhyacinth on Lake Victoria severely affected the economy, safety, and livelihoods of people and communities living along the shoreline of this huge African water body. Waterhyacinth weevils were released in an extremely successful attempt to control massive infestations of this floating weed. This program resulted in the decimation of the floating mats of this plant. However, a debate has arisen about the possible causes for the decline of water hyacinth there. Most evidence points to biological control as the major factor, but recent authors point to the El Niño associated weather pattern of late 1997 and early 1998 as the possible cause despite the very poor link between low light levels due to El Niño and significant reductions in water hyacinth growth. Reductions in water hyacinth on Lake Victoria were ultimately caused by the widespread and significant damage to plants by the weevils, but this process may have been increased by the stormy weather associated with the El Niño event. A major lake-wide resurgence of water hyacinth plants on Lake Victoria has not occurred, in contrast to predictions by advocates of the El Niño theory, and is very unlikely to occur. The population crash of water hyacinth at Lake Victoria would not have happened without the weevils, but El Niño events (primarily water movement) may have played a role.

Technical Abstract: There has been some debate recently about the possible causes for the decline of water hyacinth on Lake Victoria. The evidence points to biological control as the major factor, but the El Niño associated weather pattern of the last quarter of 1997 and the first half of 1998 has confused the issue. We argue first that there is a very poor link between low light levels due to El Niño and significant reductions in water hyacinth growth; second that increased waves and current on Lake Victoria caused by El Niño redistributed water hyacinth plants around the lake; third that the reductions in water hyacinth on Lake Victoria were ultimately caused by the widespread and significant damage to plants by Neochetina spp., but that this process was increased by the stormy weather associated with the El Niño event; and finally that a major lake-wide resurgence of water hyacinth plants on Lake Victoria has not occurred and is very unlikely. In so doing, we reiterate arguments made by Ogwang and Molo, but in the light of new supporting evidence. We conclude that the population crash of water hyacinth in Lake Victoria would not have occurred in the absence of the weevils, but that it may have been increased by El Niño events (primarily water movement).