Abstract

     This study was conducted in the laboratory of the Plant Protection Department, Faculty of Agriculture, University of Aden, during the period from 1/10/2017 to 21/1/2018, to evaluate the efficiency of plant extracts (Ricinuscommunis Ziziphusspina-christi,  Menthaspicatal), Al-Sabr plant (Aloe vacillans), Sage (Azadirachtaindica), treated with alcohol (ethanol) and warm distilled water for fighting  the bacteria that causes soft rot disease for potato tubers. The  bacterial isolation was obtained from potato tubers infected with soft rot, using  the disc diffusion method in the experiment.
     The results showed that the plant extracts varied in the extent of their inhibitory effectiveness of the bacteria causing the disease (Erwinia carotovora).
Results showed that the Azadirachtaindica leaves extract achieved the highest rate of inhibition in all repeaters (repeater 1,   repeater 2, repeater 3) and in all concentrations (10%, 20%, 30%) in both types( alcoholic and aqueous) in inhibiting a diameter of (14 mm of alcohol at a concentration of 30%) and 10.8 mm of aqueous at a concentration of 30%.
     The extract of Ricinuscommunis leaves also achieved an inhibition rate in all repeaters (repeater 1, repeater 2, repeater 3) and concentrations (10%, 20%, 30%) in both types (alcoholic and aqueous) in inhibiting a diameter of 13 mm for alcoholic at a concentration of   30% and 9.3 mm for aqueous at a concentration of 30% as well as the extract of Menthaspicatal leaves that showed an inhibitory ability in an alcoholic extract at a concentration of 20% and  30% with a diameter  of 8.2 mm and in aqueous extract with a diameter of 7.8mm at a concentration of 30%, as well as extract of Ziziphusspina-christi leaves achieved inhibition rate in all repeaters (repeater 1, repeater 2, repetition 3) and in concentrations 10%, 20% and 30% in both types (alcoholic and aqueous) with a diameter of 11.9 mm for alcohol and 9 mm for aqueous, while Aloe vacillans achieved the lowest inhibition rate in all repeaters and concentrations except inhibition rate in repeater 3 with a diameter of 8 mm at a concentration of 30% in the alcoholic extract.