A method and compounds are described and claimed relating to plant defense inducer compositions and compounds, and to their use for improving certain aspects of plant and crop management, including treating plant disease, improving the ability of plants to defend against disease, reducing disease symptoms, treating HLB disease, minimizing crop yield decreases due to plant disease, improving crop productivity, and increasing crop quality. In particular, the compounds and compositions are useful for controlling and treating plant disease, for example Huanglongbing disease (HLB) and mitigating disease symptoms of HLB and Ca. Liberibacter infection in plants. Crop plants are contemplated for use with the invention, for example citrus trees. Methods according to embodiments of the invention involve treatment of affected plants by application (preferably by injection into the trunk, soil application or foliar spraying) of one or more compounds selected from β-aminobutyric acid or a salt thereof, 2-deoxy-D-glucose, salicylic acid or a salt thereof, oxalic acid. Typical methods involve application of a composition containing a botanically acceptable vehicle and β-aminobutyric acid. In certain methods, the plants used in the method are citrus plants, and the citrus plants are affected by or susceptible to Huanglongbing (HLB) disease or infection by Candidatus Liberibacter species.
