The efficacy of some abiotic agents such as chitosan (CHT), xanthan gum (XAN), propolis (PROP) and propiconazol fungicide at its recommended dose (0.25 ml/l) against barley net blotch disease caused by Drechslera teres (D. teres) were evaluated. In vitro trials, CHT proved high inhibition effect on spore germination than on the linear growth of D. teres, while the contrary occurred by PROP. Meanwhile, XAN had not exhibited any direct effect against mycelial growth and spore germinations. In vivo trials, under greenhouse conditions, disease responses at both seedling and adult stages were significantly reduced compared to the control. Both tested concentrations of CHT and propiconazol treatments revealed the highest protection level by reducing the number and rate of lesion increase followed by XAN. Treatments of PROP showed the lower protection level especially at seedling stages. The ability of tested substances to trigger physiological defense reaction in plant tissues was investigated during the assessment of some defense related enzyme activities i.e. peroxidase (POD) chitinase (CHS) and phenylalanine ammonialyase (PAL). The higher activity of POD was obtained by propiconazol, followed by XAN at 0.3% and PROP at 0.6%. Activities of CHS showed the highest stimulation response with PROP at 0.6%, CHT at 0.1 and 0.15%, followed by XAN at 0.3%. However, the lowest response was recorded with the propiconazol. PAL activity was observed to be high in plants treated with propiconazol followed by CHT at 0.1 and 0.15%.