ASSESSMENT AND MANAGEMENT OPTIONS OF TWO-SPOTTED SPIDER MITE (TETRANYCHIDAE: Tetranychus urticae KOCH) ON POTATO (Solanum tuberosum L.) IN EASTERN HARARGHE, ETHIOPIA

Abstract

Potato is an important tuberous vegetable crop in Ethiopia. It is production is constrained by arthropod pests, nutrient depletion of soil and diseases. Among the arthropod pests, two-spotted spider mite (TSSM) is one of the major pests affecting potato production in eastern Hararghe, Ethiopia. To tackle this problem, the survey was undertaken to assess the status of TSSM on the irrigated potato. The data were collected from ninety-six potato producers from October to March in Haramaya, Kombolcha, Kersa and Metta districts by interviewing, observing and recording in 2018/2019. The meteorology data were obtained from the National Meteorological Agency, Jijiga station. The survey data analysis was made by descriptive statistics and SPSS. The assessment of TSSM was confirmed that it was found in all the districts. Data on farmer’s perception showed that 60% of the producers recognized TSSM. Based on the observation and response of the respondents, the TSSM was mostly prevailed and affected the potato production during flowering (44.2%) stages and highly incident in autumn (44.79%) season. The linear correlation coefficient indicated that the incidence (r=0.546, Y=-0.548X+38.7), number of TSSM/potato plant (r=0.847,Y=-0.06.232X+38.24) and severity level (r=0.431,Y=-0.0221X+2.805) was decreased as rainfall intensity increased. Investigation of management of TSSM by application of botanicals and synthetic pesticides was conducted in the laboratory and greenhouse. The experiment was arranged in CRD which was replicated five times in the greenhouse and four times in laboratory. In laboratory Azadirachta indica seed oil, Tagetus minuta leaf oil, A. indica and T. minutaleaf aqueous extracts, Amitraz, Profenofos and Emamectin benzoate at three dose levels and their LC50 by leaf disk spraying and dipping bioassays were evaluated. Similarly, in greenhouse Azadirachta indica seed oil, Amitraz, Profenofos and Emamectin benzoate (EB) in theircombinations and alonewere evaluated. The data was recorded at 24, 48, and 72 hours in the laboratory after application of the treatments. But the applications of the treatments were conducted at weekly intervals for three weeks and data were collected before and after the spray. The laboratory results indicated that the highest percentage mortality of TSSM adult was recorded with EB at 80μL (74-97%), followed by profenofos 35μL (71-90%), while Amitraz 80μL caused the lowest (58-83%). From the evaluated botanicals A. indica seed oil at 5% caused the highest percentage of TSSM adult mortality (72-100%), followed by T. minuta leaf oil at 5% (74-92%) inlaboratory bioassay. Amitraz caused the highest percentage mortality of TSSM eggs (72.5-92.5%) and it required 24.35μL to kill 50% of eggs, which was lower than EB (54.146 μL) and profenofos (12.737μL). Among the botanicals, A. indica seed oil had the highest toxicity against TSSM adults (2.14%), followed by A. indica leaf oil (2.31%). Furthermore, T. minuta leaf oil had higher toxic effects on TSSM eggs (0.239%) than A. indica seed oil (1.162%). The greenhouse results indicated that the combination of half dose of Amitraz and EB, one-third dose of Amitraz, EB and profenofos, and half dose of profenofos and EB resulted in better reduction (100%) of TSSM adults, immature and eggs than their sole application. It is hoped that this research would help for potato producers to manage TSSM. Further research is suggested for future work under mutiple fields locations