In Tamaulipas, a recent citrus black fly (cbf) infestation is causing some problems for producers. The combined effects on the tree of blackfly feeding and the associated sooty mold can result in serious fruit yield reductions. Producers usually manage these problem through biological control, but apparently something went wrong and disrupted that process. Pesticides were found to be ineffective in controlling CBF . The objective of this work was know the biological efectivity of Acetamiprid 20WP on A. woglumi in Valencia orange, in the municipality of Guemez, Tamaulipas. The used design was random block with five treatments (three Acetamiprid 2.0WP. 60, 80, 100 gria/ha, Dimetoato 3 l/ha and one treatment control) with four repetitions. Sampling at 30 days after application showed differences among treatments. Tukey test indicated than the 60 gr ia/ha Acetamiprid 20WP treatment presented the least number of nimphal stages 30 days after treatment. It was conclude that CBF populations in this citrus zone are susceptible to Acetamiprid.