The toxicity of Vikane (sulfuryl fluoride) to age groups of eggs of the Mediterranean flour moth (Ephestia kuehniella)

Tests were carried out on carefully aged eggs of the Mediterranean flour moth at 15 and 25 degrees C at various concentration levels of sulfuryl fluoride and over various exposure times. Eggs aged 1-2 days were more tolerant than other age groups, followed by 2-3 day-old, 0-1 day-old and 3-4 day-old eggs. At 15 degrees C 1-2 day-old eggs needed a ct (concentration x time) product of about 4000 mg.h/l to prevent hatch and 3000 to prevent emergence. Other age groups were controlled by about 3000 and 2000 mg.h/l respectively. Increasing the temperature from 15 degrees C greatly increased the efficacy of the fumigant. At 25 degrees C 1-2 day eggs needed a ct product of about 1000 mg.h/l to prevent hatch and 800 to prevent adult emergence. Other age groups required about 800 and 650 mg.h/l respectively. Considerable variation among age groups was apparent in the slopes of regression lines for the toxicity tests, whether time or concentration was fixed in the tests. There was evidence of line curvature, data sets based on different mortality ranges giving different results for calculated LD values. For example, those based on low or medial responses would sometimes grossly exaggerate the dosages required for high levels of mortality. At both 15 degrees C and 25 degrees C, fixing concentration or time of exposure in the analyses resulted in comparable results for calculated mortality levels provided that the data points included the full range of mortality response up to 100%, (C) 1999 Elsevier Science Ltd. All rights reserved.