The study on the effect of manure application and other cultural practicesrnon the infestation level and damage of Thrips tabaci on onion was conductedrnin Cheha Woreda, Luke Kebele of the Gurage Zone from December to Aprilrn2005. The field study was on the impact of manure application and plantrnspacing on the infestation level, damage, size and number of leaf and bulbrnyield were carried out on the demonstration site, and where as the effect ofrnorganic manure application on onion thrips density was based on cagernexperiments conducted using Complete Randomized Design (CRD) in fivernreplications. The field experiments was performed using a RandomizedrnComplete Block Design (RCBD) involving six treatments from a factorialrncombination of organic manure application, plant spacing and untreatedrncontrols.rnThe results on the effect of organic manure application on onion thripsrndensity indicated that, the lowest number of adult and larvae T. tabaci wasrnobtained from onions planted on soil with manure application beforerntransplanting. The highest density of onion thrips was recorded from thernuntreated controls.rnThe investigation on the impact of manure application and plant spacing onrnthe infestation, damage levels, size and number of leaves of onion revealedrnthat starting from 45 days after transplanting treatments with beforerntransplanting manure application (BTMA) at 20x30cm and 20x25cm showedrnlower mean count of thrips per plant, and highest leaf size followed by therntreatment at transplanting manure application with 20x30cm plant spacing.rnThe damage level was identified as mild at 15 and 30 days afterrntransplanting and at older stages intermediate damage was recorded onrnmost plants. On the other hand, the control treatments with 20x20cm andrn20x25cm plant spacing had the highest infestation, with the smallest leaf sizes and characterized by intermediate damage at early stages and severrnattack as the crop matured.rnThe study on the effect of organic manure application in cage experiments,rndemonstrated that the lowest mean number of larvae and adults werernobtained from manure application before transplanting followed by atrntransplanting manure application and the highest being the control with nornmanure application.rnThe survey on alternate host range of onion thrips in the study area showedrnthat five cultivated vegetables, a cereal crop and one wild plant were foundrnto harbor the insect pest on their leaves. The highest number of thrips perrnplant and percent total infestation was recorded from onion followed by Kalern(Brassica oleracea L.var acephala) and wild Sorghum (Sorghumrnarundinaccum). Finally, the survey on impact of the system on thernoccurance of predatory beneficial insects showed that, three differentrngeneralist insects and spiders were encountered in the field feeding on onionrnthrips larvae and adult.rnFinally, this study emphasized on a new strategy of managing onion thripsrnin which host plant spacing and nutrient management were integrated tornsuppress the pest population and improved the crop health and vigority tornwithstand the damage to a certain limit.