A. Monkiedje et al., Assessment of the acute toxic effects of the fungicide Ridomil plus 72 on aquatic organisms and soil micro-organisms, ENVIRON TOX, 15(1), 2000, pp. 65-70
The acute toxic effects of Ridomil plus 72 (Ridomil), used as a fungicide i
n agriculture, were studied under laboratory conditions. These effects on f
reshwater cladoceran (Chydorus eurynotus) and freshwater fish (Oreochromis
niloticus) were determined using standard bioassay procedures. The 4 h LC50
for Chydorus eurynotus was 6.9 mg/L and the 96 h LC50 for Oreochromis nilo
ticus was 1.1 mg/L. The toxicity of Ridomil to a mixed population of soil m
icro-organisms was measured using oxygen uptake and growth as measured by t
urbidity. At short-term exposure (48 min), Ridomil was moderately toxic to
the culture at 5000 mg/L and above, based on an activity quotient (AQ) of 0
.50-0.70. For longer exposure periods (up to 6 h), Ridomil was slightly tox
ic to the culture at 200 to 500 mg/L. At 1000 mg/L, Ridomil was moderately
toxic and at 3000 mg/L and above, Ridomil was extremely toxic to soil micro
organisms. The toxicity of metalaxyl tone of the two active ingredients of
Ridomil) to these micro-organisms was measured using growth as measured by
the turbidity change. The average toxic endpoint (16 h IC50) was 1100 mg/L.
The acute toxic values of Ridomil found in these studies were much below t
he expected environmental concentrations resulting from normal applications
of the chemical on a cocoa tree as a fungicide. (C) 2000 by John Wiley & S
ons, Inc.