an excellent point in stating that more research funds should be chan-

neled towards the particular objective of reducing pesticide loss at the

site of application, and many of the authors seem to share His opinion.

Since the results have demonstrated that aerially applied: herbi-
; Cides do, indeed, enter the stream system, whether as a result of direct
Spray, overspray, drift, leaching, or run-off during heavy rains, the

t

herbicides used in chemical spray programs should be formulations that

4 are the least toxic to nontarget organisms. Sears and Meehan (1971)
reported that Applegate et al. (1957), conducted toxicity tests on

rainbow trout (Salmo qairdneri Walbaum) and found that 5 ppm of @ butyl

ester of 2,4-D was lethal to this particular species. Therefore, a
lesser dose could be expected to be toxic to rainbow and more importantly,
detrimental effects among aquatic invertebrates may quite conceivably
“result from substantially lower doses than that reported. Buty? esters
of 2,4-D and 2,4,5-TP have been found to be 100 times more toxic than
their corresponding acids; however, one redeeming factet ts that they

are quickly hydrolyzed to the acid or salt under field conditions

(Norris et al. 1970). The results of the stream monitoring program show
that in some cases the herbicide residues were still present for at.

least 72 hours, whether or not this can be considered as short term

exposure Still remains questionable.