The aphid and mealy bug are insects that attack the cotton plants at the beginning and final life cycle of the culture. This work aimed to study the population fluctuation of aphid (Aphis gossypii) and mealy bug (Planoccoccus sp.) in different upland cotton cultivars in Fortaleza-CE. The evaluation of the infestations was made through observations in the field every week. The number of plants infested by mealy bug and aphid was recorded every seven days when the plants had at least one colony of the species. The presence of aphids was noticed on the 20th day after the germination of the plants and the infestation started reducing gradually on the 41st day. The mealy bugs were noticed about 48 days after the germination of the plants and the infestation started reducing from the 85th day. The results indicated that the aphids infested the plants during the sixty days of plants life, while the mealy bug infestation happened between 50th and 100th day.
