To study the effect of jasmonates (JAs) on the resistance of economic forest plants to insects, Rosa rugosa ’Plena’ leaves were treated with 1 mmol/L jasmonic acid (JA), methyl jasmonate (MeJA) and Z -jasmone, then the content of tannin and total phenol in leaves and the feed-ing area of Monolepta hieroglyphica adults on leaves were measured. Changes in the activities of detoxification enzymes in adult M. hieroglyphica that had fed on leaves treated with JAs were also studied. Tannin and total phenol levels in leaves increased significantly after treatment with JAs, and tannin level was 1.36–1.55-fold higher than in the control after treatment with 1 mmol/L MeJA. The total con-tent of phenol in leaves treated with 1.0 mmol/L Z -jasmone increased by 1.33–2.20-fold compared with those of the control. The activities of detoxification enzymes in adults were inhibited to differing degrees: activity of alkaline phos-phatase (AKP) first increased, then decreased; the activities of acid phosphatase (ACP), glutathione S-transferases (GSTs) and carboxylesterase (CarE) following treatment with 1 mmol/L MeJA were significantly reduced and were 22％–31％, 11％–26％, and 11％–31％ lower than those of the control, respectively. Moreover, the feeding area of adult M. hieroglyphica on the leaves treated with JAs was sig-nificantly reduced ( P < 0.05). The feeding area of economic forest R. rugosa ’Plena’ leaves treated with 1 mmol/L MeJA decreased by 17％–43％ compared with that of the control. Moreover, the decrease in the adult M. hieroglyphica feed-ing area was highly positively correlated with the content of tannin and positively correlated with the contents of total phenol of economic forest R. rugosa ’Plena’ leaves. The reduced feeding area of adult M. hieroglyphica was highly negatively correlated with the activities of AKP and ACP and negatively correlated with those of the GSTs. In conclu-sion, the use of 1 mmol/L MeJA can noticeably decrease the deleterious effects of adult M. hieroglyphica.