A field experiment was conducted at AL-Ramadi / AL-Anbar province in 2005 to investigate the effect of thermal degradation of dursban in controlling of aphids(Myzus persicae) on cucumber .The insecticide was exposed to six temperatures levels in the laboratory (0 , 5 ,10 , 20 , 40 and 60 0C) for five exposal periods (1 , 2 , 4 , 6 and 8 h) In infestation % of aphids and productivity were estimated. Results showed that dursban activity was decreased at (0 0C)with increasing exposing temperatures whereas infestation % was (25 %) at (60 0C) , up to (9 %) at (0 0C) lead to decrease productivity of plant with increasing temperatures .The higher average obtained under (5 0C) was (3352 kg/D) , while it decreased at (60 0C) of (2819 kg/D).