These studies were made to clarify the effects of treatments for winter protection-rice straw covering, straw mat covering, net covering, vinyl film covering, vinyl and straw mat covering, vinyl covering, OED green spraying, machine oil emulsion spraying, binding and control-on preventing defoliation of citrus thees through winter and also to investigate the wintering status of straw mat covering and in treated citrus trees planted on the trial fields at different altitudes between 100 and 400 meters above sea level on Cheju-do.
The results are summarized as follow:
1. Rice straw, straw mat, net, binding and vinyl straw mat were effective in avoiding cold injury of citrus trees. But vinyl covering made many leaves fall than the control. There was no significant difference among each of OED green, machine oil emulsion and the control.
2. Straw mat and net were most effective in protecting the trees from cold damage and there was no significance between them.
3. Up to the present, the net for winter protection has never been applied to citrus culture on Cheju-do. But according to this study, its effect on preventing defoliation was excellent and it was more economical than straw mat.
4. In the experiment at different altitudes, there was severe defoliation at hight altitudes especially 400 meters above sea level and the protecting effect of the covering treatment was more remarkable in unfavourable environment.
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