AbstractInjection of cucumber cotyledons with polyacrylic acid (PA), acetylsalicylic acid (ASA) and salicylic acid (SA) induced resistance to inoculations withColletrichum Iagenariumwhen inoculation followed injection by 96 h but not by 24 h. Size and number of lesions were greatly decreased. Resistance was greatest in injected cotyledons but was also pronounced in non‐injected halves of cotyledons and occasionally in first or second leaves.Incorporation of PA, ASA and SA into liquid shake cultures did not significantly affect growth of the pathogen.Gel electrophoresis of soluble proteins extracted from cotyledons showed that induction of resistance was not accompanied by the appearance of novel soluble protein