| Abstrakt: |
One of the major usages of pesticides is in programs to control forest pests. In North Amerime up to eight million hectares have been sprayed in a single year. The total amount of pesticide used in eastern Canada against spruce budworm, over the period 1952 to 1979, exceeds 16 million kilograms. The assessment of the effects of these programs on nontarget organisms is bedeviled by many factors: nonuniform deposit of pesticides, changes in population due to nonpesticide causes, effects of weather on population assessment. The threshold dosage of fenitrothion causing mortality of songbirds is 280 g/ha. Phosphamidon at 140 g/ha caused heavy mortality of birds, but 70 g/ha did not show significant effects. For orthene the level causing mortality appears to be 280 to 560 g/ha although the data base is small. Most studies of sevin indicate no problems with dosages as high as 2.2 kg/ha, although one detailed study found marked effects at 1.1 kg/ha. The dosage levels of aminocarb, dimilin, and dylox causing harm to birds has not been determined but are in excess of 168 g/ha, 280 g/ha, and 1.1 kg/ha, respectively. Although dosage-causing mortality has been determined for several pesticides there is little information on long-term population effects. |
