The mean phosphine concentration observed at the time corresponding to one-half of the
calculated egg development time was compared to the lethal concentration (LC99) for a 2-day exposure
at each temperature±moisture combination. In the low-moisture grain at 208C, the observed fumigant
concentration was below the lethal concentration, due to the long development time under these
conditions. At 25 and 308C in the low-moisture wheat, the likelihood of complete kill appeared more
favorable because the fumigant concentration remained above the published LC99 for more than half of
the egg development time.