(24(3-4):43-54)DISCOVERY AND STUDY ON THE BORON DEFICIENCY OF PAPAYA

本研究目的，在於明瞭近年來臺灣各地木瓜果實普遍發生畸形怪病，果面凹凸不平呈瘤塊狀之原因何在？自民國62年至63年，先後在木瓜主要產地屏東縣高樹、鹽埔兩地進行各種試驗，探究其發生原因及防治方法。先用尋袋及噴藥防治，斷定其業非病蟲為害，繼之進行各種肥料施用量、施用法及灌溉試驗，以及莖部解部、組織切片。葉片及土壤分析，指示植物檢定及田間試驗等結果，始證明為缺硼症。其病徵為果實先流乳漿，繼而呈凹凸不平瘤塊狀，果腔胎座及未成熟種子之假種皮呈淡褐色，且種子多不發育或不充實。用硼砂每株0.5公克，濃度0.25%行葉面噴施；或用硼砂每株2.5~5公克行土壤施用，即可完全防止木瓜缺硼症之發生。 An unknown disease was wide spread in papaya orchard recently. Latex secretion was found on the surface of fruits at first, and then many tumors were formed. The whole area in the location including young seeds was turned into brown color. The fruits after attacked lose their marketable value. Boron deficiency was found after many investigations and experiments under JCRR project and Chung-cheng Scientific Technology Foundation. Leaf samples collected from papaya trees with deformed-fruits contained only about one-fourth concentration of boron of the leaves from healthy trees. Tomato and Lettuce grown in soils collected from diseased fields developed typical boron deficiency symptoms. The disease was controlled by spraying leaves of diseased trees with 0.25% borax or 0.1% boric acid solution or by applying 0.5% borax around a diseased trees. Results indicated that deformed-fruit disease of papaya was caused by boron deficiency. In the same time, we found that it is much easier to cause boron deficiency if papaya trees are planted in the sandy soil during the dry season. Boron in sandy soil is easy to wash off after rainning but is not easy to be absorbed by plant when soil is dry. Therefore, regular irrigation and application of borax is necessary in papaya orchard