樹病判別指南 How To Determine Tree Diseases

謹記：正確的診斷樹木是一個繁瑣但必要的程序。

原作者：JOHN C. FECH－2015.8.6

Diagnosis. It’s something that we do every day, from figuring out why the toast didn’t pop up to what that letter from the IRS actually means. For our purposes in the arboricultural world, it’s best to think of diagnosis as a process; a process by which many “influencers” are examined to determine the specifics of what appears to be a disease.

「診斷」是我們每天都在做的事，從搞懂烤吐司機為何沒有跳起來到解讀一個沒見過的英文縮寫。以樹藝的目的而言，我們最好把診斷理解成一個過程：檢查多個影響因子來判別那些疑似疾病的特性。

There are diseases and then there are non-diseases… at least not in the classical sense. Better stated, both living (biotic) and non-living (abiotic) factors can cause a diseased condition in trees.

有疾病就有「非疾病」，非疾病指的是那些不符合傳統定義上的樹病。更準確來說，樹病的發生可以歸因於生物及非生物因子。

So, why is so much emphasis put on the precursors and definitions? Well, if we skip to the bottom line, there are consequences of the result/determination of the cause or causes. The result of the process will determine the best course of action for a particular tree—fungicidal treatment, improvement in growing conditions, neither, or both.

之所以在前言跟定義上大費周章的說明，是因為倘若省略了這個重要的部分，可能會導致某種結果，進而引發嚴重的後果。診斷樹病的過程也是如此，必須先查明疾病的成因，能採取適切的處理，例如真菌處理、改善立地環境、兩者兼施甚或是不予處理。

First steps, second steps…

一步一步來…

The process of diagnosis has many steps. As such, it pays to take the time to work deliberately in a step-by-step approach rather than being in a hurry and quickly jumping to conclusions. Overall, the procedure is general to specific, and described below:

樹病診斷分為好幾個步驟，並不能快速而急躁的做出結論，必須投入大量的時間循序漸進地進行繁瑣的檢測。這個推論的程序是從一般到個別，由抽象到具體的，詳細說明如下：

Macro-look at the surroundings: The location of a tree in the landscape is of primary concern. As I was beginning my career, a wise arborist explained the value of walking a neighborhood to gain a sense of place and context for a tree’s malady instead of walking straight up to the specimen. The influential factors to consider in this first step are wind patterns, slopes, history/age of the development and client’s property, evidence of changes in grade, human and vehicular traffic patterns and condition of surrounding trees.

巡視周圍環境：對於一棵樹，我們首要關注的是它在地景中所處的位置。在職業生涯之初，一位有智慧的樹藝師向我說明：比起直接視察樹體，走訪鄰近區域、了解地方特性更有助於查明樹木發病的經過。在這第一步驟中，需要考量的因素包括氣流、坡度、地區發展的歷史及政策、地勢改變的證據、人車來往的交通型態，以及周圍樹木的狀況。

Macro-look at the tree: A tree is a large, living organism; it has roots, a trunk, flowers, fruits, stems, bark, conductive vessels, heartwood, sapwood and many other tissues. In order for the tree to be healthy, all must work together. After the macro-look at the surroundings, an “eyes-wide-open” circular loop around the specimen is a good second step. Walking 360 degrees is helpful; part B of the macro-look at the tree is the vertical, up-and-down view. This is best done with the help of binoculars, which helps to bring the far away up close, usually allowing you to see symptoms that ordinarily would not be visible such as cracks, insect holes and peeling bark.

綜觀整棵樹：樹木是一種大型的活有機體，具有根、樹幹、花、果實、莖、樹皮、導管、心材、邊材及其它多種組織。這些組織共同運作來維持樹體的健康。在巡視周圍環境過後，第二步該做的是睜大眼睛360度繞著整棵樹看一圈，接著沿垂直方向上下掃視，最好以雙筒望遠鏡輔助，以觀察樹冠高處那些肉眼難以辨識的裂痕、蟲孔、樹皮剝落等病徵。

Focus on the soil and rooting area: Half of the tree’s tissues are underground…half! If diagnosticians only look at the leaves and stems, they would be ignoring potential sources of pathogens and abiotic problems. In addition, the soil structure and fertility level is paramount for stability and providing essential elements for photosynthesis. If the area surrounding the tree is unsuitable, keep this in mind as the process rolls along.

細看土壤及根系：樹木組織有一半埋在地底，如果樹木醫只看枝葉來進行診斷，將會忽略許多潛在的病原體及非生物因子。此外，土壤結構及肥力對於樹體的穩定及光合作用所需地養分是至關重要的。如果周圍環境不適合樹木生長，後續的判斷及處理必須將此納入考量。

A focus on the rooting area begs the question, “how big is the rooting area?” The quick answer is 1,000 square feet. Is that a real answer for every tree? No, but an average tree in an average landscape ought to have at least 1,000 square feet of healthy soil to grow in.

根系拓展的面積有多大？快速地回答是1000平方英呎，但這能適用於每棵樹嗎？不能，這是假設一顆平均的樹生長在至少含有1000平方英呎健康土壤可生長的情形下所得到的數字。

Hone in on the trunk: The trunk is the portion of the tree responsible for half of the tree’s water movement and structural integrity. If this area is compromised due to pathogens or abiotic issues, it becomes a major limiting factor. Cracks, which are serious because they are physical separations of bark, cambium and sapwood, usually lead to pathogenic diseases, such as cankers, and, often, insect invaders.

細看樹幹：樹幹肩負了樹木半數以上的水分疏導及結構強度，如果樹幹遭受病原體或非生物危害，將會形成樹木健康主要的限制因子。開裂是樹木健康的嚴重問題，其意味著樹皮、形成層及邊材物理性的分離，經常導致病原性疾病，裡如潰瘍（canker）以及昆蟲入侵。

Move up to the branches: Next on the list are the branches. Crossing limbs, broken limbs (hangers) and oozing tissues are worthy of note and possible action. Binoculars are a must when looking into the tree canopy at the branches.

續看枝條：接著我們來看枝條，交叉枝、斷枝（懸掛枝）及分泌物值得記錄並採取可能的處理。觀看樹冠枝條通常需要望遠鏡來輔助。

Finish at the foliage: When “tree disease” is mentioned, the foliage is usually the first thought in most minds…it should be the last, at least to ensure consideration of each of the first five steps. Foliage is important for photosynthesis, transpiration, respiration and shade for the property owner. Every leaf is significant for these reasons; if something out of the ordinary is observed, such as a spot, split or dark blotch, further investigation is necessary.

以葉片作結：提到樹病，多數人最先想到的是葉片，但在檢查時它應該被放在最後，至少是在前五項步驟完成之後，葉片很重要，它有著光合作用、蒸散作用、呼吸作用以及提供遮蔭等功能。因此每片葉子都應該被重視；一旦觀察到葉斑、破裂、葉枯等病徵，都必須進行後續的追蹤檢查。

Disease triangle

樹病害三角

Normally reserved for managing tree diseases, the disease triangle can be helpful for diagnosing them. Really? Sure, if you look at all three sides – Environment, Host, Pathogen – each has unique characteristics that can help determine what may be causing the tree in question to decline…or at least narrow it down some.

對於樹病診斷，樹病害三角是一個好用的工具：環境、寄主、病原體各具有獨立的特性，從這三個角度切入，有助於判定樹木健康問題或衰弱的原因，或至少限縮可能的因素。

Environment: The weather conditions and elements in the landscape can have a profound influence on the likelihood of tree disease. For example, cool and moist conditions are conducive for foliar pathogens such as sycamore anthracnose. Likewise, hot, dry and windy conditions are the common cause of abiotic problems such as leaf scorch, which often is confused with a fungal disease.

環境：天候狀況或者地景的各種因素深刻影響了樹病發生的機會。舉例來說，涼爽潮濕的天候容易發生梧桐炭疽病；而炎熱乾燥的天候經常導致日燒病等非生物危害，經常與真菌疾病相混淆的。

Host: Each tree species has a set of infectious diseases commonly associated with them. When considering the host, it’s absolutely essential that you back up a step and are sure of the identity of the host species. Once the identity is confirmed, it’s very helpful to start with the common problems of the host. For example, crabapples are commonly infected by fireblight, apple scab and cedar apple rust, while Austrian pines often are diagnosed with dothistroma needle blight and diplodia tip blight. Information on specific diseases of each species can be found at university extension offices as well as nearby arboretums and botanic gardens.

宿主：每種樹有各自相對應的一系列常見傳染病。探討宿主的影響時，首先必須要能準確地辨識樹種。一旦確認宿主的樹種，便可以從該物種常見的問題開始著手。例如蘋果屬植物常見的病害有火燒病、黑星病、膠鏽蟲癭等；南歐黑松則經常出現松針紅斑病及針枯病。特定物種與對應疾病的資訊可以在大學及鄰近的實驗林及植物園取得。

Pathogen: Various pathogen groups – i.e., the cankers, the leaf spots, galls, wilts, root rots, decay organisms – have a characteristic appearance. As you consider this part of the disease triangle it helps to be familiar with the general form and shape of each. One of the best ways to do so is to simply go to an image search engine such as Google Images or Yahoo Image Search and type in “tree cankers” or “heartwood decay symptoms.” Such a search will provide a basic “look” of the pathogen group.

病原：種類多樣的病原各有特色獨具的風貌，包括潰瘍、蟲癭、葉斑、凋萎、根腐及腐朽菌等。熟悉各種病原的樣貌對於應用在樹病診斷上是非常有幫助的，Google、Yahoo等搜尋引擎的圖片搜尋功能是很好用的神器。嘗試輸入如黑腐病(tree cankers)、心材腐朽(heartwood decay symptoms)等樹病相關的關鍵字可以快速的找到這些病原類群的基本外型。

Abiotic factors: Roughly 50 percent to 60 percent of all of the “tree diseases” I encounter are caused by nonliving organisms. This is not to say they are unimportant and shouldn’t be treated; rather, it just means that there is often more than meets the eye. When abiotic factors are present, they often stress a tree sufficiently to lower its resistance to biotic diseases such as mildew, anthracnose, decay and cankers.

非生物因子：以作者的經驗來說，有五到六成的「樹病」是由非生物因子所造成的。這並不表示它們不重要或不需要處理，而是意味著很多樹木問題是我們眼睛看不到的，當非生物因子出現問題，經常對樹木的生存產生壓力，使得樹木對黴病、炭疽病及腐朽非生物性病害的抵抗力降低。

A few of the more common abiotic diseases are:

一些樹木常見的非生物性危害

Girdling roots: Often caused by planting too deeply or a failure to loosen tangled roots that were created by a plastic pot/B & B root ball, roots that cross each other or press on the trunk basal plate create a weak point, sometimes leading to root starvation, heartwood decay, borer invasion and overall tree decline.

盤根：經常發生在種植時覆土過深或利用塑膠盆或美植袋移植樹木時並未把纏繞的根系舒展開來的情況，根系互相交疊、壓迫到樹幹基部而產生脆弱點，有時會導致根系營養不良、心材腐朽、蟲蛀以及樹勢衰弱。

Lack of a root flare: Another good sign that the tree was planted too deep, the lack of a root flare usually is manifested by the tree entering the ground with the same trunk diameter as the lower scaffold limbs. Deeply planted trees often struggle due to lower-than-necessary gas exchange function, as well.

缺乏根領：這是種植過深的另一個徵兆，一棵缺乏根領的樹，通常具有以下兩個特徵：一、主幹與土壤連接處沒有直徑加大的現象；二、側枝較低。種植過深的樹木通常也會有氣體較換不足的問題。

Soil compaction: Heavily trafficked sites often produce a root zone where soil particles are pressed together so much that roots cannot move throughout easily. These root systems do not develop sufficiently to extract moisture and nutrients and/or provide structural support.

土壤壓實：在人車往來頻繁的立地，土壤顆粒經常被壓密結塊而使得根系不易穿透，這類根系通常發育不良而難以提供足夠的水分、養分及結構支撐。

Trunk bark damage: Whether from lawn mowers, weed eaters or juvenile delinquents, bark damage is highly consequential. When this occurs, decay organisms gain an entrance point to the cambium and sapwood, leading to degradation and the interruption of nutrient/water flow.

樹皮損傷：無論是割草機或人為破壞所造成的樹皮損傷都會對樹木健康造成很深的影響。包括形成層、邊材的腐朽入侵，進而導致養分及水分運輸中斷。

Irrigation system defects: Plugged, broken or misaligned drip and overhead irrigation system components can wreak havoc with the moisture and oxygen content in the soil, keeping the tree roots too wet or dry.

灌溉系統故障：滴流灌溉／灑水系統的阻塞、破裂或調控失常會導致土壤的含水量及含氧量嚴重失衡，使樹木根系處於過於乾燥或濕潤的狀態。

Springtime freezing or severe winter temperatures: New growth or dormant buds often are killed or weakened by these weather events. Recovery often is impossible; replanting or restorative pruning may be necessary.

春季的霜害或嚴冬的低溫：這類天氣事件經常導致新芽或休眠芽死亡或衰弱且通常無法復原，必須重新種植或實施恢復修剪。

High soil salts: Indicated by a soil test, high levels of soluble salts stunt root expansion and therefore limit uptake of nutrients and moisture as well as potential structural stability.

土壤鹽度過高：土壤實驗顯示，高濃度的可溶性鹽類阻礙了根系擴張，因而限制了水分及養分的攝取並可能降低結構的穩定性。

Again, remember that tree disease diagnosis is a process. It can be difficult and frustrating at times. Training from state arborists associations, university extension and the International Society of Arboriculture help to ease the path to success.

再次重申，樹病診斷是一套程序。它有時是困難而令人挫折的。地方樹藝師協會、大學及國際樹藝師協會提供的訓練將有助於邁上成功之路。