Controlling Water Hyacinths With 2,4-D in South Florida


 by

 J. C. Stephens, V. L. Guzman, and C. C. Sealel



 THE PROBLEM

 The Water Hyacinth (Eichhornia crassipes), a perennial aquatic weed,
is reported to have been introduced into the United States at the Cotton
Centennial Exposition in New Orleans in 1884 from South America. Native
to Japan, it thrived well in the climate of southeastern United States,
and by 1890 had invaded the fresh waters of Florida where it soon became
a widespread pest. This floating, mat-forming plant has been called the
"million dollar" weed because of its adverse effects on water control,
wildlife, and navigation. Water control is extremely difficult in a
system of infested waterways and canals. A cover of hyacinths will cut
the flow in large drainage canals to one-half of normal flow, and even
more in smaller laterals and farm ditches. Hyacinths carried by flood
waters frequently jam into dense masses at bridge piers and pump intakes
so that flow is almost completely stopped. They have been known to jam
up and push over wooden highway bridges in south Florida. Under floating
hyacinth mats the light is cut off so that submersed aquatics, some
valuable for duck food, do not grow; also, the oxygen supply in the water
is reduced to the point where only gar and mudfish survive. Navigation
is often completely blocked by a dense growth of water hyacinths.

 THE PLANT

 The mature hyacinth plant consists of roots, rhizomes, stolons,
leaves, blossoms, and fruit clusters. The broad, green leaves extending
out and up from a central axis have an enlarged basal spread or float
filled with air sacs which allows the plant to float. Erect spiked
clusters of beautiful lavender blossoms are characteristic of this plant.

 The hyacinth reproduces at an astounding rate. W. T, Penfound and
T. T. Earle2 have made an exhaustive study of water hyacinths in Louisiana
and report that under good growing conditions a floating mat of these
plants will grow outward about its periphery at the rate of 2 feet per
month, the plants doubling their numbers every 2 weeks by means of off-
shoots. At this rate only ten plants would produce about 650,000 plants


 1
 Drainage Engineer, Assistant Horticulturist, and Associate
 Agronomist, respectively.
 2
 The Biology of the Water Hyacinth, Ecological Monographs,
 Vol. 18, No. 4, October 1948.