Calculation of the Economic Injury Level (EIL) of cabbage aphid Brevicoryne brassicae L(Hem.: Aphididae) on canola Brassica napus L. Hydromel cultivar

The cabbage aphid, Brevicoryne brassicae is one of the importan pests of canola in Iran. The aphid causes significant yield losses by feeding on plant sap, particularly affecting the inflorescence and leaves. This study aimed to determine the economic injury level (EIL) and economic threshold (ET) of this aphid on the Hydromel cultivar of canola using a randomized block design with four replicates in West Azerbaijan province during the 2016-2018.The most widely cultivated canola cultivar, Hydromel was exposed to cabbage aphid feeding under natural infestation conditions in eight treatments (Ts): (T1) seven weekly Imidacloprid SC35 at 2000 PPM sprays since the beginning of the shooting stage (aphid-free); (T2) six sprays, one week after the shooting stage; (T3) five sprays, two weeks after the shooting stage; (T4) four sprays, three weeks after the shooting stage; (T5) three sprays, four weeks after the shooting stage; (T6) two sprays, five weeks after the shooting stage; (T7) one spray, six weeks after the shooting stage; and (T8) control; Full pest presence without any insecticide, only water spraying. The mean aphid population, canola yield, and thousand-seed weight in different treatments were analyzed using Duncan’s multiple range test. The regression equations were established between aphid population density and yield per square meter. Additionally, the yield loss per aphid was also estimated. The results showed that the economic injury level (EIL) of cabbage aphids in West Azerbaijan Province on the Hydromel cultivar was 6.6 aphids per 10 cm² of flowering stem per plant.