Effects of chemical inducer on the induced resistance to powdery mildew in honeysuckle _(Lonicera japonica Tunb.)

The induced resistances of honeysuckle against powdery mildew were compared at different growth ages by using chitosan, oxalic acid, salicylic acid（SA）, dextran, sodium silicate, ferrous sulfate（FeSO_(4)）, trifluralin and potassium phosphate dibasic （K_(2)HPO_(4)）. The results showed that the resistance induced by chitosan and oxalic acid was higher than that by other chemicals, with average control rates of 82.3% and 59.9%, 72.1% and 54.9%, 58.4% and 74.1% on one-year, two-year and four-year honeysuckles, respectively. The chemicals salicylic acid, dextran, sodium silicate and FeSO_(4) had instable effects, while dextran and K_(2)HPO_(4) had no induction effects. Trifluralin deteriorated the disease.