植物病害的非農藥防治品─亞磷酸

Control of Plant Diseases with Non-pesticide Compound-phosphorous acid

安寶貞( P. J Ann)

《植物病理學會刊》 10卷4期 (2001/12) Pp. 147-154

https://doi.org/10.6649/PPB.200112_10(4).0001

摘要

亞磷酸原為緩效性磷肥的一種，1980年代被發現可以防治卵菌綱引起的植物病害。爾後，有關亞磷酸防治病害的作用與防病機制一直引起學者的興趣，至今仍在探討中。一般認為亞磷酸在高濃度下（1000ppm以上）對病菌的菌絲生長與產胞有干擾與抑制作用，有直接保護（direct protection）寄主的功效，但防病功效並不完全。近年來，許多報告均指出亞磷酸有誘導植物增強抗病性的間接防病（Indirect defense）的功效，它會加速植物抗禦素、酚化合物、或其他抗病物質的產生與量的累積。至於有關亞磷酸誘導寄主產生抗病反應的全程機制尚未完全了解，其正確切入抗病反應路徑的位置亦待求證。由於亞磷酸是強酸，水溶液的酸鹼值約為pH2-3，必須以鹼性物質中和至pH5.5-6.5後，才能施用於植物體。目前在國外，亞磷酸已被開發與商品化，如Foli-R-Fos 400(20% H3PO3)，Nutri-Phite P Foliar(4% N-30% P2O5-8% K2O)。田間試驗顯示，亞磷酸對疫病菌、露菌病有良好的防治效果，經常用於酪梨根腐病、柑橘疫病、葡萄露菌病、萵苣與十字花科露菌病的防治。在台灣，一種簡單配製亞磷酸的方法已被研發出來，使用者與農民可以自行配製。其方法是將工業級的亞磷酸(95-99%)與氫氧化鉀(95%)以一比一等重使用，先將需用量的亞磷酸溶於水中，再溶解氫氧化鉀，調配好的亞磷酸的酸鹼值約Ph6.0-6.2，可直接使用，可以減少調配亞磷酸酸鹼值時的費時與費工，並避免溶液於保存時，因氧化作用而導致藥效降低的情形。目前依照上述方法，亞磷酸普遍被農民用於蘭花疫病、番椒疾病、多種作物疾病與露菌病的田間防治。

關鍵字

亞磷酸 ； 亞磷酸鹽 ； 誘導抗病 ； 植物抗禦素 ； 病害防治 ； 疫病 ； 露菌病

並列摘要

Phosphorous acid (H3PO3) and its salts (phosphite or phosphonate) are reduced phosphorus compounds, which could be used as a fertilizer. Many researchers were interested in the functions and the mechanisms of this kind of compounds on disease control since it was found to be very effective in controlling Phytophthora diseases in 1980s. Several reports, in early years, indicated that application of high concentration (＞ 1000 ppm) of neutralized phosphorous acid could directly protect plants by inhibition and interference of the myceial growth and sporangial production of Phytophthora species and other members of oomycetes. However, it was subsequently found that the indirect effect of inducing host resistance against the pathogens is a more important action contributing to the disease control. Disease reduction was found to be associated with increase in production and accumulation of phytoalexins, phenolic compounds or other antifungal substances. Currently, most researchers believes that phosphorous acid has both direct (plant protection) and indirect (host defense) modes of actions, but plant defense induced by the chemical is more important in breaking down pathogen's attack. How phosphorous acid activates the host defense reactions and which position of the pathway it effects, are still unknown. Phosphorous acid could not be directly applied to plants due to its strong acidic character (pH2-3) in water solution. It has to be neutralized to pH 5.5-6.5 with alkaline compounds such as sodium hydroxide (NaOH) or potassium hydroxide (KOH) before. lse. Commercialized products of phosphorous acid includes fungicide such as Foli-R-Fos 400 (20% H3PO3) and fertilizers such as Nutri-Phite P Foliar (4-30-8) and Guard PK (7-21-21) for diseases control. These products are commonly used for control of avocado root rot and citrus foot and root rot caused by Phytophthora species, downy mildew of grape, lettuce and crucifer and many other diseases caused by members of oomycetes. Recently, a simple method for phosphorous acid application was developed in our laboratory. It consists of dissolving equal amount (w/w, i.e. 1:1 in ratio) of phosphorous acid (H3PO3, 92- 95%, industry grade) and potassium hydrochloride (KOH, 92-98%, industry grade) in water. The pH of the resulting solution is about 6.0 to 6.2, which is not phytotoxic to plants. The major diseases successfully controlled in the fields with this technique in Taiwan included late blight of potato and tomato caused by Phytophthora infestans, blight of pepper caused by Phytophthora capsici, root rot of avocado caused by Phytophthora cinnamomi, black rot of orchid caused by PhytoPhthora palmivora and Phytophthoa parasitica, and fruit downy blight of litchi caused by Peronophythora litchii.

並列關鍵字

Phosphorous acid ； phosphite ； induce resistance ； phytoalexin ； diseases control ； Phytophthora diseases ； downy mildew