Effect of biorational insecticides on the cotton aphid, Aphis gossypii under the laboratory conditions

Abstract

The cotton aphid (Aphis gossypii, Glover) is a small sap sucking insect that belongs to the family Aphididae which is a major insect pest of various crops i.e., cotton, okra, mustard and cabbage. Present study was carried out in the Complete Randomized Design (CRD) with five replications and two different biorational insecticides including control i.e., T₁: Afidopyropen (2 ml / 500 ml water) T₂: Afidopyropen (0.5 ml / 500 ml water) T₃: Spinetoram (0.024 g­ / 500 ml water) T₄: Spinetoram (0.012 g­­ / 500 ml water) T₅: Control (500 ml water), respectively. The data shows that the highest aphid mortality was observed 100% when sprayed with T₁ (Afidopyropen) and T₃ (Spinetoram) at 5 Days After Spray (DAS), while the lowest mortality was found 34% at T₄ (Spinetoram) at 1 DAS during 1^st spray of biorational insecticides, respectively. Similarly, after 2^nd exposure of insecticides against aphid, the maximum death rate was seen 100% on T₁ (Afidopyropen) at 5 DAS, whereas the minimum was noted as 42% on T₂ (Afidopyropen) at 1 DAS, respectively. Furthermore, after 3^rd spray, the highest mortality rate was observed 100% when treated with T₁ (Afidopyropen), T₂ (Afidopyropen) and T₃ (Spinetoram) during 5 DAS, while the least mortality was seen 52% on T₄ (Spinetoram) at the interval of 1 DAS, respectively. However, moderate mortality was recorded during 3 DAS after 1^st, 2^nd and 3^rd spray of insecticides. The results further revealed that in T₅ (control), 1 to 10% mortality was observed at 1, 3 and 5 DAS during 1^st 2^nd and 3^rd spray, respectively. The analysis of variance shows a highly significant difference (P<0.01) between various biorational insecticides and DAS. It is concluded that the highest aphid mortality was observed on lethal doses (T₁ and T₃) at 5 DAS, while the lowest mortality was recorded at sub-lethal doses (T₂ and T₄) at 1 DAS after 1^st, 2^nd and 3^rd exposures of biorational insecticides.