Vol. 15—1961 - NorthEastern Weed Science Society

561.
Potential
Uses of Calcium Clanamid in the
Control of Aquatic Vegetation
J. Curtis Simes, Regional Fishery Manager
Pennsylvania FiSh Commission
The manuel removal of aquatic weeds from the trout rearing ponds and raceways
at the Pennsylvania Fish Oommissions' Benner Spring Fish Research Station
in Centre County had, prior to the 1960 season, been an operation of considerable
magnitude. The dominant aquatic weeds found in these limestone waters
include curly-leaved pondweed, Potamogeton crispus; commonwaterweed, Anacharis
canadensis; horned pondweed, Zannichellia ~alustris; duckweed, Lemnaminor;
water cress, Nasturtium officinale; and several unidentified forms of filamentous
algae. At intervals averaging about once every six "Weeksduring the main
growing sea son it had been necessary to cut and remove this growth from all
earth-bottomed ponds and r-acevaya, Scythes and pitchforks were the usual implements
employed. Substantial losses of fingerling trout frequently accompanied
these manual operations.
In mid-June, 1960, a number of ponds and raceways at this station were
drained, scraped to remove accumulated muck and food wastes, and treated chemically
with the primary objective of controlling certain fish-disease organisms.
Ivlr. Gordon Trembley, Ohief Aquatic Biologist and Mr. Arthur Bradford, Fish
Pathologist jointly prescribed and directed the sterilization procedures.
Calcium cyanamid, a readily available and commonly used nitrogen fertilizer,
was the sterilant used in roughly seventy-five percent of the treated ponds
and raceways. This gray, finely-granular material was broadcast uniformly to
the exposed bottoms at a rate approximating 100 pounds per 1000 square feet.
Schaeperclaus (1933), the German fishery scientist, has written regarding the
use of this product for fertilization and disease control in the European pond
industry. Calcium hypochlorite and chlorine were the sterilsnts used in the
remaining rearing facilities involved. By July 1, most ponds had been flushed
and refilled with water preliminary to restocking with fish. The elapsed time
between application of the sterilants and resumption of normal fish rearing
operations in the various facilities ranged from a minimumof two days to a
maximumof two weeks. In no case did the introduced trout appear to be adversely
affected by any residual activity of the sterilants used.
By late August it became apparent to some of the hatchery personnel that
the cyanamid treated facilities had remained amazingly free of weed growth as
opposed to those treated with the other chemical products. I~nual removal of
weed growth had to be resumed in the raceways treated with calcium hypochlorite
and chlorine by early September. ObserVations up to the end of October revealed
that the calcium cyanamid treated areas were, with only one minor exception
completely weed free.
This unanticipated success in controlling or retarding aquatic weeds
through the application of cyanamid to exposed bottoms prompted the initiation
of several supporting experiments. To explore the potential of t.ht~ mAt,nrlAl