Field evaluation of plant oil formulations as potential control measures against the cotton mealybug (Phenacoccus solenopsis Tinsley)

The cotton crop is heavily infested by various insect pests, including Phenacoccus solenopsis. Antagonistic plants offer an alternative source of insect biocontrol agents because they contain various bioactive materials, many of which are selective or have no adverse effects on non-target organisms or the environment, unlike synthetic insecticides. Therefore, three locally available plant oils were tested to evaluate their efficacy in reducing P. solenopsis in cotton fields. Statistical analysis showed a highly significant difference (DF = 3, 23; F = 194.42; P = 0.0000) for the reduction of the P. solenopsis population. After the first spray, the highest overall mean reduction of P. solenopsis (61.26±10.69%) was recorded in the cotton plot sprayed with neem oil, followed by castor oil (50.11±10.94%) and mustard oil (38.30±8.39%). After the second spray, the highest overall mean reduction of P. solenopsis (70.01±9.26%) was again observed with neem oil, followed by castor oil (50.51±8.90%) and mustard oil (40.06±8.74%). Furthermore, results concluded that neem oil achieved the highest reduction of P. solenopsis population (84.45%) on the third day, with an overall reduction of 65.64±9.94%. The second-highest reduction (68.96%) with an overall reduction of 50.31±9.9% was recorded in the plot sprayed with castor oil, followed by mustard oil, which reduced the population by 54.05% with an overall reduction of 39.18±8.55%. The results also indicate that the efficacy of neem oil remained effective until the third day after spraying, while on the seventh day, the P. solenopsis population began to increase gradually.