Evaluation of some botanical extracts against two-spotted spider mite (Tetranychidae: Tetranychus urticae koch) under laboratory condition

Abstract

Two-spotted spider mite (tssm) (Tetranchus urticae koch), is the most devastating polyphagous sap-sucking pests of many vegetables, fruits, cereal crops, and ornamental plants. tssm is the major pest of potato in Eastern Hararghe, Ethiopia. The present study was conducted to evaluate the potential of Azadirachta indica seed and leaf oil, Tagetes minuta leaf oil and their leaf aqueous extracts against tssm in the plant protection laboratory of Haramaya University. Amitraz 20 EC was used as a standard check in the experiment. The experiment was arranged in a completely randomized design (crd) in four replications. Treatments were applied on adults of tssm both by spray and dipping methods, while only dipping method was used on the eggs of tssm. The number of tssm dead adults was recorded for three days (72 hrs) at 24 hrs intervals, while egg mortality was recorded 12 days after treatment application. The mortality percentage was corrected using Abbot’s formula before data analyses. Significant differences (P<0.05) were observed among the treatments both in adult and egg mortality of tssm. The highest mortality was obtained with Amitraz 20 ec (95.5-100%), followed by A. indica seed (90.125-94.95%) and T. minuta leaf oil (78.5-84.5%) in spray and dip bioassay 72 hrs after treatment application. The least effective treatments were A. indica leaf aqueous leaf extracts (AqE) (56.125%) and A. indica leaf oil (55.45%) in spay and dip bioassay 72 hrs after treatments application. The highest mortality of tssm eggs was obtained from the application of Amitraz 20 EC and A. indica (92.28%), followed by T. minuta leaf oil (83.74%). The lowest mortality (21.34%) and highest hatching (78.66%) of tssm eggs were recorded from the application of leaf aqueous extracts. The study also revealed that mortality of tssm was clearly time-dependent i.e. mortality increased proportionally with increase in time after treatment application. The study revealed the promising efficacy of A. indica seed oil and T. minuta leaf oil that were comparable to Amitraz 20 EC in the management of tssm under laboratory condition.