Vol. 16—1962 - NorthEastern Weed Science Society

workers. springer (1961) cite8& numberof references and gives values as
low as 1 ppmfor d.amageto bluegills by the butyl:'ester. Other esters
were less toxic and the sodiumsalt was tolerated.~,by rainbow trout at eollcentrations
up to 112 ppm. It is thought that in somecases add1tivesand
impurities mayaccount for muebot the observed fi,h mortalities.
457
Noreferences have been found that give toxicity of 2,4-D to the eastern
oyster, the blue crab, the softshell clam or commonspecies of estuarine
fish. The presence of inorganic'salts in seawater'may possibly a.lter the
toxicit1 of 2,4-D compoundsto a species of fish Ill, salt water as comparedto
the samespecies in fresh water. IA series of experiments is underwayat
Solomonsto determine the toxictt,of the bl4tOxy ..ethanol-ester used in:ollr
field tests upon the economically11l1portantestuat1ne, animals in both fresh
and saltwater aquaria.
A preliminary series of observations on cage4ranimals was madein the
Machodocduring July and August of 1960 (Beaven, 1960). In that series. no
lethal effects were detected upon oysters, crabs or fish at the centers of
three plots each receiving a different formulation··of 2,4_Dat 40 lb. AE/A.
A fourth formulation at 20 IbsoAE/A, however, killed all animals in the
cl18e. These tests all were madeduring higher walter temperatures than In
1961 and with plants moremature. Milfoil control was poor. In the plet
where the animals died, the treatment produced little noticeable kill of
milfoil and anaerobic conditionfwere not a factor. It was postulated that
toxic impurities in the formulation caused the observed animal losses.
In late June of 1961 an adlH.honal one.acre treatment of JOIbs. Af./A
and a control were placed in the LowerMachodoc.lData from these are not
included in the preceding tables since they were not directly comparable to
the others' due to the later appl1tation. Fifty d*1s after treatment, all
oysters in both plots were aUTe, 2 crabs survivelin the treatment co.red
with 0 in the control, and 8 fish survived the treatment comparedwith 9 in
the control.
.~
Although data for crabs are 'weak, the resuQt~of the studies to date
indicate that the formulation of 2,4-D used, whenapplied in a similar manner
at concentrations of JOlbs.AEVA or less, does not·directly cause a sl8hlfi­
,cant .mortality amongthe econeetc.'forms exposed, iner amongthe observed!.
native bottom fauna.
A serious threat, howevel',·til oysters, clams-:and other bottom org!llAisms
'is evident in treated areas~en large mats of decomposingmilfoil remain
upon the bottom. Parallel kills. 'of native fish. Cl' crabs maynot occur !in a
small plot, even though those caged in the anaerobic plot did die. As free
swimmers,these animals can moveout of locally unfavorable areas and it is
noteworthy that, though liVing abundantly in surrounding water, no native
fish or crabs were found as dead specimens in the plot. However,if dense
milfoil beds over an entire creek are killed, with subsequent anaerobic development,
it is possible that a heavy mortality of fish and crabs in it
mayfollow.
.