Experimental Analysis of Ecomomic Action Level of Tomato Leafminer, Tuta absoluta Meyrick (Lepidoptera: Gelechiidae) on Tomato Plant under Open Field

Tomato leafminer, Tuta absoluta (Meyrick) is considered to be one of the major pests of tomato crop in Ethiopia. In tomato, economic impact is caused by larval which feeding leaves and fruits. Information on tomato leafminer economic injury levels (EILs) and economic thresholds (ETs) is relatively limited. Studies were conducted during 2015 to 2017 to determine EILs and ETs on open field is required for more effective management. The results from the current studies significant (P<0.05) differences were observed among the treatments during the study periods. T. absoluta was highly infested the untreated control as compared with protected treatment. The mean value of marketable yield loss to the cost of insecticide application at one larva/plant was 3.61% and from untreated control was obtained 77.91% during 2015/16. Similarly, during 2016/17 at one larva/plant and untreated control marketable yield loss were observed 5.57% and 81.61%, respectively. The highest yield loss was observed at unsprayed control (24,577.84 kg/ha) followed by five larvae/plant (10,587 kg/ha) during 2015/16 while during 2016/17 the highest yield loss also observed in untreated control (26,593.08 kg/ha) followed by five larvae/plant. From this study the economic injury level of T. absoluta was 3.82 larvae per plant. Therefore, based on economic injury level, the economic threshold level was determined as at 2.87 larvae per plant.