Abstract
Onion thrips (Thrips tabaci L.) is one of the most important serious insect pests of onion (Allium cepa L.) cultivation in Ethiopia. The present study was conducted to evaluate some botanical extracts viz. Artemisia annua, Azadirachta indica, Bidens pilosa, Chrysanthemum cinerariaefolium, Cymbopogon citratus, Nicotiana tabacum, Nicotiana spp.,(local var.,), Parthenium hysterophorous, Phytolacca dodecandra, Securidaca longepedunculata and two indigenous isolates of entomopathogenic fungi (EPF) viz. Beauveria bassiana (PPRC-56) and Metarhizium anisopliae (PPRC-6) and soap detergent powder. They were examined for controlling onion thrips (Thrips tabaci L.) under field condition in Guder, Toke Kutaye district of Ethiopia from mid October 2010 to early April 2011. Diazinon 60% E.C was applied at the recommended rate of 1.8 l/h and the plot left was examined as controls. After 1st day application of the different agents, EPF and untreated control were not significantly different. However, the results on 3rd, 5th, and 7th day after application of EPF treatments indicated that highly significant mortality. The rate of mortality in all of the treatments after 1st day ranged from 0 to 74.75%. On the other hand, botanical extracts recorded at 3rd day of application ranged from 26.09 to 74.75% within 3days of the higher mortality was recorded. On 5th and 7th day, except B. bassiana (PPRC-56), the mortality rate in all treatments became declined. The results indicated that insecticidal actions of all the tested agents exhibited to the ranging from 26.09 to 74.75% against onion thrips. Of the different agents, Nicotiana spp., P. dodecandra, S. longepedunculata and N. tabacum exhibited high mortality rate (69.65, 68.99, 63.85 and 63.56%, respectively), whereas in C. cinerariaefolium, A. indica and P. hysterophorous showed intermediate mortality rate (60.79, 56.89 and 52.06 respectively) and the rest were the lowest mortality rate. High bulb yield reduction was recorded in untreated plots but low yield reduction was observed in treated plots and control check. The treatments also showed reducing onion thrips population and also gave significant control over the treated check. This study indicated that Nicotiana spp., P. dodecandra, S. longepedunculata, N. tabacum and B. bassiana were significantly very effective against onion thrips under field condition at recommended rate and then confirmed the valuable rate of botanicals and EPF as components of Integrated Pest Management (IPM) practices in Ethiopia.
Highlights
Allium crops are the most indispensable vegetable crops used as condiments in most Ethiopian cuisine
This study was conducted under field condition at Guder area in Toke Kutaye district of West Showa Zone, Oromia Regional State, Ethiopia
Significant differences among the treatments were observed after application of botanicals and entomopathogenic fungi (EPF) agents and the results are depicted in tables 2,3 and figure 7
Summary
Allium crops are the most indispensable vegetable crops used as condiments in most Ethiopian cuisine. Onion (Allium cepa L.) is one of the oldest known and an important bulbous vegetable crop grown in Ethiopia. It is used in preparation of different foods and in therapeutic medicine in the country. Toke Kutaye district of West Showa Zone, Ethiopia has high potential for onion cultivation due to availability of ample irrigated farmlands and the presence of relatively better market access as compared to other districts of West Showa Zone. Farmers in the study areas are growing the varieties of Adama red and Bombe red. Both varieties are susceptible to onion thrips
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