EFFICACY OF PESTICIDES ON TWO-SPOTTED SPIDER MITE (Tetranychus urticae Koch) (Acari: Tetranychidae) AND ITS PERFORMANCE ON SOME HOSTS AT HARAMAYA, EASTERN ETHIOPIA

Abstract

The study was conducted in Plant Protection Laboratory and greenhouse (GH) at Haramaya University under 25±2 oC, 70±5% RH and 30±2 oC, 60±5% RH, respectively, during 2016. The objectives were to: 1) evaluate the efficacy of some pesticides on Tetranychus urticae in the laboratory and greenhouse; and 2) evaluate the performance of TSSM to six plants under GH conditions. The efficacy of five pesticides, viz. Amitraz, Profenofos, Chlorantrniliprole + λ-cyhalothrin, and Profenofos"Q"720 g/l, @ manufacturers’ rates and Paraffin oil @ 2.5%, were evaluated, in the laboratory, while the GH study, in addition to the five pesticides applied alone, rotation of Amitraz with the other four pesticides evaluated. All the studies were arranged in CRD, and replicated five and four times in laboratory and GH, respectively. The laboratory study on adult TSSM was conducted by leaf disc spraying and dipping. Adult mortality was recorded 24 and 48 hrs after treatment. For ovicidal study leaf disc spraying and dipping were used. In both methods, data were recorded up to nine DAT. Based on 48 hrs observations on adult TSSM, all treatments applied by leaf dipping showed highly significant (p ≤ 0.0001) difference over the control. All pesticides caused 100% mortality except Paraffin oil that resulted in 96.41% mortality; likewise 48 hrs later, adults treated by leaf disc spraying, with all the pesticides showed highly significant (p ≤ 0.0001) difference over the control provided 100%, mortality except Paraffin oil that inflicted 85.90% mortality. The pesticides caused higher egg mortality using leaf dipping method and showed highly significant (p ≤ 0.0001) difference over the control, provided mortality of Amitraz (99.00%), Profenofos (92.96%), Chlorantrniliprole + λ-cyhalothrin (91.28%), Profenofos "Q"720 g L-1 (90.14%) and Paraffin oil (86.82%). Egg mortality using lesf disc spraying method showed highly significant (p≤ 0.0001) difference over the control, caused mortality of Amitraz, Profenofos Chlorantrniliprole + λ-Cyhalothrin, Profenofos"Q"720 g/l and Paraffin oil resulted in 99.14, 92.12, 89.78, 87.94, 84.92%, respectively. For the GH study, the results after third spray indicated a highly significant (p ≤ 0.0001) difference between the treatments over the control. A week after third spray, all the treatments provided 100% reduction of all stages of the mite. In the T . urticae performance test, six plants were studied and replicated thrice. Two-spotted spider mite counts were recorded until four weeks beginning two weeks after infestation. There were a highly significant (p ≤ 0.0001) difference in the number of mite population among the xv hosts. Solanum incanum, Datura stramonium, and S. tuberosum had statistically non significant population size though the mite population on the hosts vary and were in order of performance. But these plants differed significantly from S. lycopersicon, Capsicum spp. and P. vulgaris. Therefore, the study showed that all the tested pesticides were effective to suppress TSSM and gave opportunity to use them in rotation to slow or prevent resistance development. But, it needs careful research under farmers’ field conditions. Leaf disc spraying and dipping identified pesticides and both were effective methods for screening. The study revealed that Capsicum spp. was least preferred while S . lycopersicon and P. vulgaris were intermediate in status; however, S. incanum, Datura stramonium, and S. tuberosum were the most preferred hosts. To this effect, host plants like Solanum incanum and D. stramonium should be removed from farm boundaries as these weeds are potential shelters of the pest. Further study is required on other hosts, especially on weeds as documented materials are not available on Ethiopian conditions to manage the pest.