Ea. Harrahy et al., THE EFFECTS OF DIFLUBENZURON (DIMILIN(R)) ON SELECTED MAYFLIES (HEPTAGENIIDAE) AND STONEFLIES (PELTOPERLIDAE AND PTERONARCYIDAE), Environmental toxicology and chemistry, 13(3), 1994, pp. 517-522
Two types of laboratory toxicity tests (exposure in water and feeding)
were conducted to determine the effects of diflubenzuron (DFB) on non
target aquatic insects. The mayflies Cynygmula subaequalis, Stenacron
interpunctatum, Stenonema meririvulanum, and Stenonema femoratum (Hept
ageniidae) and the stonefly Peltoperla arcuata (Peltoperlidae) were ex
posed to DFB in water for 96 h, then transferred to pesticide-free wat
er and observed for 36 d. The mayflies were exposed to 0, 0.6, 5.6, 55
.7, or 557.2 ppb and the stoneflies to 0, 1.0, 10.2, 101.5, or 1,015 p
pb DFB in water. The mayflies were found to be sensitive to DFB in wat
er at concentrations as low as 0.6 ppb. The stonefly was less sensitiv
e to DFB in water. In our feeding studies, Peltoperla arcuata and Pter
onarcys proteus (Pteronarcyidae) were fed DFB-treated yellow poplar le
aves for 24 d, then observed for 60 and 90 d, respectively. Survival o
f treated Peltoperla was significantly different from the controls at
day 60. Survival of treated Pteronarcys was not significantly differen
t from the controls during the 90-d test period, although the low numb
er of molts that occurred during that time may have influenced these r
esults. Future studies should use early life stages that coincide with
leaf fall, when treated leaves would be introduced to headwater strea
ms. The life histories of many aquatic insects are timed to make maxim
um use of leaf detritus as a food base. Introduction of DFB-treated le
aves to headwater streams may adversely affect these organisms.