highly significantP < 0.001
This treatment difference in week 4 of the second generation was already highly significant ( F 1,118 = 42.13, P < 0.001) and it had become absolute by 8 weeks, when nymphs were entirely absent from all the populations exposed to 2.7% rifampcin and 11 of the 16 populations exposed to 0.9% rifampicin.