Cotton aphids are a potential problem for future cotton systems. Their abundance in different cotton seasons is strongly influenced by the availability of over-winter hosts, hence in the recent dry years they have generally riot been as much of a problem as they were in the years following the wetter winters of 1998 and 1999. Consequently, a change to wet conditions would see the potential for high aphid numbers earlier in the season again. This poses a risk to cotton for several reasons. Firstly, because the effect of aphids on the Growth and yield of cotton is poorly understood. Secondly, because aphids are vectors of Cotton Bunchy Top disease. Finally, because aphids are increasingly resistant to some of the insecticides used for their control, notably pirimicarb (carbamate) and most of the organophosphates (dimethoate, omethoate, profenofos, chiorpyrifos). Over the past three years we have completed experiments to determine if aphid populations affect cotton growth and yield. Such information can provide the basis for development of thresholds for control. However, it is also important to obtain information on aphid ecology and distribution that will help in developing more robust management strategies. For this reason we have also monitored the use of alternative hosts by aphids, their distribution within cotton field and within plants. In addition we also interested in the carry-over of resistance from one year to the next.