ACUTE TOXICITY OF PROPANIL,ORDRAM AND FURADAN TO CRAWFISH (Procambarus clarkii) WHEN CHEMICALS WERE COMBINED AND USED ALONE1

In laboratory studies, acute toxicity tests (96-hour) showed strong main effect on crawfish when Propanil, Ordram, and Furadan were combined; this combination was the most toxic treatment to crawfish. Furthermore, a strong interaction among the three suggests a non-additive response. Ordram alone was the least toxic pesticide. Additive effect was observed when Furadan was combined with Ordram or Propanil, but antagonism was detected in the combination of Propanil with Ordram. Concentrations higher than the recommended rate for use at normal conditions had a significant (P<0.05) lethal effect on crawfish. Soil moderated the toxicity of some pesticides and their combinations.