Abstract
A new disbudding method using a water jet nozzle was developed. An experiment was conducted on 32-year-old satsuma mandarin trees (cv. Okitsu wase) bearing many fruits. The disbudding treatment was applied to selected lateral shoots 1 day after budding (March 31, transverse bud diameter: 1.24 mm), 7 days after budding (April 6, transverse bud diameter: 2.30 mm), 16 days after budding (April 15, transverse bud diameter: 2.86 mm), or 24 days after budding (April 23, transverse bud diameter: 4.99 mm). Two types of nozzles with different discharge volumes (WJN1: 43.8 mL/s; WJN2: 29.3 mL/s) were considered for the bud removal rate and time required. As a result, NNZO12 was more successful for removing buds. When the nozzle with the higher discharge volume (WJN1) was used 1 day after budding, the time required was 49.5% of that needed for manual disbudding, and the removal rate was 96%. Because the peduncle became thick with time, the time required to remove buds increased; from these findings, it was considered that the treatment up to 7 days after the sprouting (bud diameter 2.3 mm) was effective for disbudding using the water jet nozzle. No significant difference was found in the required time when the treatment was applied more than 7 days after budding. The development of new shoots could be damaged if the water jet disbudding was applied to very small buds just after sprouting.
