Vol. 15—1961 - NorthEastern Weed Science Society

540.
The oontrol plot was ohosen somewhat south of the experimental
area, at a distanoe great enough to be unaffeoted by diffusion.
Between the dates June 8-10, preoeding the applioation of the
Aqua Gran~lar on June 29, preliminary observations were made and
sampling was carried out. After the applioation, this routine of
observation and sampling was repeated at intervals throughout the
season, namely JUly '1, July S, July 20, and September 15. Samples
were taken at random from eaoh plot and the oontrol. In eaoh
plot the bottom temperature was reoorded, a water sample from the
bottom was obtained, and two hauls for benthio organisms were
made wi than Eokman dredge. A plankton haul was also made and
standardized as well as possible by rowing 3 times aoross the
plot. The oontents of the dredge were sieved, identified, and
oounted in the field. The plankton was taken direotly to the
laboratory where it was identified under a binooular disseoting
miorosoope. The water samples also were oarried immediately to
the laboratory where determinations of pH and 02 in ppm were made
by the use of the Hellige Testing APparatus.
On June 29, the Aqua Granular was applied by hand from a
rowboat. As the granules were soattered from the boat, most of
them sank sloWly to the underlying weeds, or fell to the bottom
mud if that was unoovered.· Some granules remained on the lily
pads for a day or two but eventually fell into the water.
Granules were obvious in the water for 4 or 5 days and some were ­
visible even a week after the application •
. The six experimental plots were treated as follows. Three
plots reoeivedgranules of 10% 2, 4-D aoid equivalent, at a concentration
of 0.9 ppn, 1.,3 ppm, and 1.8 ppn. The other three
received granUles of 20% 2, 4-D aoid equivalent at aoonoentration
of 1.8 PPm, 2.6 ppm, and 3.6 ppm. In both series the bulk rate
was So lbs./aore, 75 Ibs./acre and 100 lbs./aore. .
. Since the immediate results of the applioation of the
granules Were similar for all plots, a general description appropriate
,for all will be given. On the first day after the
application, the typioal reactio:t) pegan. Lily pads developed
brown spots and began to ourl; flowers looked Wilted; petioles
appeared slightly longer. On the seoond day, the reaotion was
intensified. The lily pads were ourling, and due to the
elongated petiole, overturning. By the sixth day, the pads and
stems presented a tangled mass of vegetation. The numerous
elongated and arohed petioles together with the overturned pads
gave a definite red cast to the plots. Both stems and leaves
were decaying rapidly. At this point it was obvious that
Nymphaea and Brasenia had reoeived lethal doses of 2, 4-D.
However, 'no opinion on the condi tion of submergGO.vegeta tton
could be advanced.