Control of bacterial spot on plums by sprays of calcium oxytetracycline and copper and infusion with N-pyrrolidinometbyl tetracycline

Bactericides were evaluated on Golden King and Redgold plums for the control of ba~terial spot disease caused by Xanthomonas campestris I?v. pruni. Full-cover sprays of calcium oxytetracycline (COT) and of copper compounds in combination with spray lime (1:1 ratio) were applied from 90 % petal fall to harvest. Golden King trees were infused with N-pyrrolidinomethyl tetracycline (PMT) 6 mo before commencement of spray treatments (autumn). COT sprayed weekly at 90 g produ~t1I00 ~m3 water control~ed the di~ease sign!ficantly on fruit and foliage of Redgold. However, COT was meffectIve on Golden Kmg. Cupnc hydroxide (weekly at 50 g and fortnightly at 100 g/l00 dm3) and copper oxychloride (fortnightly at 200 g/l00 dm3) were superior to COT on both cultivars. InfuSion ofPMT by micro-injection (2,5 g product/tree) was comparable with or more effective than certain copper treatments. No visual damage was observed on trees.