An 'on farm' research was conducted in the La Vega province in 2008 with the objective to evaluate the adequate moment (5, 15, 25 days after germination, dag) to initiate a program of applications against aphids and other vectors of viruses in longyard beans. In a randomized trial with four blocks and seven treatments (T) were compared: T1=untreated check, with two commonly used insecticides: the systemic Thiamethoxam (T2=5 dag, T4=15 dag, T6=25 dag) and Diafenthiuron (T3=5 dag, T5=15 dag, T7=25 dag). To adjudicate the effect to the initial applications, from the 32nd dag all plots (T1-7) received similar applications by the farmer. The studied variables consisted in presence and severity of virus symptoms, fluctuations of arthropod populations and yields (weight of fruits, exportable and rejects). Results obtained: a) The check was more affected by the presence and severity of symptoms of viruses during the first four evaluations; b) from the 6th evaluation on, there was no longer any difference between the treatments; c) concerning the counts on sticky traps, no statistic differences were measured, nevertheless, there was a tendency of a higher control of aphids and whiteflies in Thiametoxam-treated plots (15 dag); d) in the same, the yields of 1st quality fruits was superior to the rest; e) concerning the weights of rejected or total of fruits, the check yielded less than the treated plots.