Insects, mites, and plant pathogens as agents of waterhyacinth (eichhornia crassipes(mart.) solms) leaf and ramet mortality

Abstract

The effects of insect and mite herbivores and plant pathogens on waterhyacinth leaf and ramet mortality were studied at Canal-M, Palm Beach Co., Florida, from December 1981 to January 1983. Individual ramets were tagged in December 1981 and again in May 1982, then monitored to determine rates of leaf production, proportional amounts of damage by various organisms, and ultimate causes of leaf and ramet mortality. Only the moth Sameodes albiguttalis(Warren) and the weevils, Neochetina bruchiHustache and N. eichhorniaeWarner, caused reduced leaf longevity. Other organisms were sporadic or restricted to old leaves. About 74 percent of the first group of tagged ramets were killed. S. albiguttaliskilled 31 percent by late April, then ceased to be effective due to changing plant morphology. Neochetinaspp. killed 42 percent, and mortality was relatively constant. Neochetinaspp. killed about 33 percent of the shoots tagged in May. We conclude that S. albiguttalisis effective for control of waterhyacinth in only very restrictive circumstances. The weevil N. eichhorniae, and to a lesser extent N. bruchi. are more effective biocontrol agents. The demise of the waterhyacinth population was predictable from a comparison of leaf production and leaf mortality rates. The relationship between herbivore persistence and the plants’ ability to replace damaged tissue mediates the resiliency of waterhyacinth populations. © 1987 Taylor & Francis Group, LLC.