Cotton aphid, Aphis gossypii Glover, remains an annual pest of cotton in Louisiana and other Mid-Southern states.  Until recently, this insect has been of minor importance and insecticide oversprays were occasionally required against heavy infestations.  During 2006 and 2007, excessive numbers of cotton aphids were detected on cotton seedlings, and in some fields, persisted on plants well into the flowering period.  Recommended insecticides, primarily the neonicotinoids, failed to provide consistent control in many of these fields.  The results of field trials and laboratory tests suggest that some populations of cotton aphids may be expressing a change in susceptibility to neonicotinoids.