抄録
The objective of this study is the development of a defoliation technology for pear trees by spraying salt water. The effects of the concentration of the NaCl solution on defoliation were investigated. The defoliation period of Japanese pear ‘Shinko’ treated with 3 ％ NaCl solution was the same as 6 or 10 ％ NaCl solution, and the leaves of those treated were lost earlier than those of the control（NaCl solution of 0 ％）. However, the promotion effect on the fallen leaves by the NaCl solution was not seen on European pear ‘Le Lectier’. To clarify the influence of early defoliation by spraying salt water on tree growth, elongation of the shoots, growth of fruits and starch content of the branches were investigated. In previous years, the adult trees of Japanese pear ‘Hosui’ and ‘Shinko’ were treated with 6 ％ NaCl solution in 2009 and 2010. The defoliation of the branches of two pear cultivars were promoted by spraying the NaCl solution. In 2010, elongation of the shoots on Japanese pear ‘Housui’ and ‘Shinko’ showed little difference. However, in 2011, elongation of the shoots of ‘Hosui’ and growth of fruits of ‘Shinko’ treated with NaCl solution were clearly reduced. The starch content was investigated by a simple assay method. The starch content of the shoots was decreased by early treatment of NaCl solution. These results show that early defoliation was caused by spraying the NaCl solution. In addition, these findings suggest that accumulation of starch content and the growth of pear trees in the following year might be affected by second consecutive year treatment with the NaCl solution.
