E. M. Stafford

The Vapor Toxicity of Certain Bromopropanes to the Grape Phylloxera under Controlled Laboratory Conditions

Standard laboratory procedures were developed in which first instar nymphs of the grape phylloxera Phylloxera vitifoliae (Fitch), were used to determine the toxicity of selected brominated propanes. Tests were conducted in sealed soil columns and soil-free vessels. At 70° F., with or without soil, 1,3-dibromopropane was the most toxic member of the series tested which included 1-bromopropane, 1,2-dibromopropane, 1,2,3-tribromopropane and 1,2-dibromo-3-chloropropane (Nemagon® or Fumazone®). In the absence of soil, the order of toxicity based on the weight of fumigant per liter fit ED50 was 1,3-dibromo>1,2,3-tribromo>1,2-dibromo-3-chloro> 1,2-dibromo> 1-bromo. With the exception of 1,3-dibromopropane, the order of toxicity was reversed when the dosage was expressed as relative vapor saturation at ED50. In the presence of soil, the order of toxicity based on the weight of fumigant at ED50 was the same as that based on relative vapor saturation in the absence of soil. Because of their low thermodynamic activity (relative vapor saturation) 1-bromopropane and 1,3-dibromopropane appeared to be acting as chemical poisons. The toxicity, of the other three propanes indicated their activity to be that of physical poisons. Either in the presence or absence of soil, the order of toxicity of 1,3-dibromopropane at different temperatures was 85° F. >70° F., >55° F. Excessive dosages of 1,3-dibromopropane failed to kill nymphs in soil of 5% moisture content. This fumigant was more effective in soil of 22% moisture content than in soil containing 15% moisture.