Standard curves for nuvacron, malathion, sevin, DDT and kelthane tested against the mosquito Culex pipiens L. and the microcrustacean Daphnia magna Straus.

The fourth instar larvae of Culex pipiens L. and adults of microcrustacean Daphnia magna Straus were reared under standardized conditions and used as bioassay test organisms for the preparation of the standard log concentration--probit (lc--p) regression lines for each of the following pesticides: nuvacron, malathion, sevin, DDT and kelthane. When the above pesticides were tested against the larvae of C. pipiens, the LC50 values (in ppm) ranged as follows: nuvacron 0.0014--0.0019, malathion 0.0027-0.0043, sevin 0.059-0.095, DDT 0.233-0.525, kelthane 0.17-0.24 and a mixture of malathion, DDT and kelthane (3 : 10 : 5) 0.1805-0.2451, based on 24-h readings. The corresponding LC50 values (in ppm) for D. magna were 0.00018-0.00032, 0.000074-0.00013, 0.00063-0.00069, 0.0061-0.0064, 0.071-0.090 and 0.055-0.028 for the aforementioned pesticides. D. magna proved to be more sensitive to all tested pesticides than C. pipiens larvae: it succumbed to concentrations ranging from 0.000032 to 0.004 ppm of nuvacron, from 0.000032 to 0.0016 ppm of malathion, from 0.000032 to 0.02 ppm of sevin, from 0.0008 to 0.1 ppm of DDT, from 0.03 to 0.3 ppm of kelthane and from 0.007 to 0.075 ppm of the mixture. C. pipiens larvae were affected by concentrations ranging from 0.0005 to 0.008 ppm of of nuvacron, from 0.0005 to 0.04 ppm of malathion, from 0.008 to 1.0 ppm of sevin, from 0.05 to 2.5 ppm of DDT, from 0.06 to 0.5 ppm of kelthane and from 0.07 to 0.75 ppm of the mixture.