Fruit tree trunk diseases are a set of pathological conditions that affect the woody part of the plant, compromising its health and productivity. The pathologies can manifest themselves in different forms, from fungal infections to bacterial diseases, up to attacks by xylophagous insects that cause significant damage to the woody tissues. In the most serious cases, the presence of fruit tree trunk diseases can lead to the death of the plant, and put the survival of those nearby at risk.
Precisely for this reason it is very important to regularly monitor the health of fruit trees, intervening promptly in the event that some of the main symptoms that could hide the presence of a trunk pathology are manifested. Careful and constant observation allows early identification of signs such as abnormal cracking of the bark, the presence of exudates or gums, discoloration of the wood, or the presence of fungal fruiting bodies, making effective monitoring particularly important in the most critical periods such as the spring vegetative recovery and during the summer water stress phases.
Let’s see together what the main diseases are and how we can prevent and cure them.
Cortical cancer or cancer of the cortex
Cortical cancer, or bark cancer, is a dangerous disease caused by fungi such as Cryphonectria parasitica or Nectria galligena, particularly aggressive pathogens capable of attacking various tree species, with a particular predilection for plants of the Castanea genus. Other fruit trees such as apple, pear and cherry can also be susceptible to the infection.
In our country the disease spread mainly after World War II, becoming well established throughout the Peninsula. A rapid expansion probably favored by the stressful conditions of plants in the postwar period, to which the reduced attention to phytosanitary management of forests at that time contributed.
Its most typical manifestation is that of widespread lesions on the bark that tend to widen visually: irregular patches, often brick-red in color, that later result in the swelling of the bark and its tearing, allowing glimpses of the dead tissue beneath. The lesions may initially appear as small depressed or slightly raised areas, then evolve into true wounds that impair the functionality of cortical tissues.
Removing the infected bark, you will be able to see at the edges of the living tissue the presence of creamy yellow mycelial felts, positioned in a fan shape, for a characteristic arrangement of the fungal mycelium that is an important diagnostic sign to identify the disease. At this point, the tree will try to heal the destroyed tissue, resulting in cortical necrosis (cancers). In the rest of the tree, the leaves will tend to shrivel but remain hanging on the affected branches, due to a phenomenon that is caused by the interruption of lymphatic flow due to the death of vascular tissue in the cancer-affected area.
The treatment of bark cancer involves removing the infected parts with tools sterilized by flame or 70% alcohol, in order to avoid the spread of the disease, and applying protective mastics to the wounds. It is essential that the intervention is timely and accurate, eliminating all the infected tissue until reaching the healthy wood. The cuts must be clean and oblique to facilitate the flow of rainwater and avoid stagnation that could favor new infections.
In addition to direct treatment, it is important to take preventive measures such as proper pruning management, avoiding unnecessary and uncontrolled wounds, and maintaining a good vegetative state of the plant through appropriate agronomic practices. In some cases, the use of antagonistic fungi such as Cryphonectria hypovirus, which can help naturally contain the disease through a phenomenon known as hypovirulence, may be useful.
Collar rot
Collar rot is a very dangerous fungal disease if not intercepted and treated promptly. Determined by the fungus Phytophthora cactorum, the disease occurs in the collar area, causing browning of the bark at the base of the trunk and root rot. The pathogen is particularly insidious; in fact, it can survive in the soil for long periods through the production of resistant spores called oospores, which are activated under favorable conditions such as high humidity and mild temperatures. The infection can affect many species of fruit trees, with particular incidence on apple, pear, peach and cherry trees, causing significant economic damage in commercial orchards.
Unfortunately, Phytophthora infections are quite difficult to manage and, for this reason, prevention remains by far the most effective way to reduce the impact of the risk of infestation. Correct soil management, control of irrigation practices, monitoring plants for timely identification of signs of disease presence, are essential to reduce the probability that your plant is affected by the phenomenon. Effective preventive management to contain the risks involves choosing resistant rootstocks, using certified propagation material and carefully preparing the soil before planting, ensuring good drainage and avoiding water stagnation. It is also important to maintain a correct distance between plants to promote aeration and reduce relative humidity in the surrounding environment. Periodic analysis of soil pH and maintenance of optimal levels of organic matter can help create conditions less favorable to the development of the pathogen.
If, on the other hand, symptoms have already appeared, action can be taken with soil drainage, reduction of irrigation at the base, and treatments with copper products.
In this sense, it is very important to note that the first symptoms can be subtle and include a general decline of the plant, yellowing of the leaves and reduction of growth, before the more obvious signs appear, such as the presence of gummy exudates at the base of the trunk or the detachment of the bark in the collar area. Curative interventions must be timely and integrated: in addition to improving drainage conditions, specific fungicides authorized for this pathogen can be applied, preferably as a preventive measure in the seasons most at risk.
In severe cases, it may be necessary to remove the soil around the collar to promote aeration and drying of the infected tissue, followed by the application of healing pastes containing copper. Post-operative management is crucial and requires constant monitoring to prevent any recurrence, with particular attention to irrigation management and the health of the surrounding soil.
Wood decay
Wood decay is another disease of the trunk of fruit trees that can have very serious repercussions on the life of the plant and can lead to a rapid process of degradation of the cells of the internal wood. The disease represents one of the main causes of structural deterioration of mature fruit trees, compromising not only their productivity but also their mechanical stability and the safety of the orchard.
Caused by certain fungi that are able to penetrate into the interior of the tree through trauma wounds (such as those that arise as a result of branch breakage caused by excessive snow load or pruning that is poorly done), it is characterized by a gradual weakening of the tree brought about by the expansion of fungal populations, which feed on the woody tissue of the plant. The main fungal agents responsible belong to the genera Fomes, Trametes and Ganoderma, which possess specific enzymes capable of degrading lignin and cellulose, the main structural components of wood. Progressive degradation creates internal cavities that can extend along the trunk and main branches, impairing the tree’s ability to transport water and nutrients.
The disease is quite common and, unfortunately, manifests obvious symptoms when it is often already late. It is therefore very important to try to intercept early signs of pathology promptly, such as the presence of fungal fruiting bodies on the trunk, before which prompt action should be taken by desiccating some portions. Other early signs may include the presence of cavities in the trunk, areas of depressed or dead bark, and the appearance of woody tissue of altered color, often lighter or darker than normal. The emission of exudates or the presence of xylophagous insects may be additional indicators of an ongoing decay process.
Restoration through suction of carious wood is a difficult operation and does not guarantee good results. However, it is possible to try this route if the disease has not affected large parts of the trunk. Next, disinfect the cut with specific copper-based products. It is, of course, essential that this operation be carried out with special care, using approved products and following the correct application procedures.
Prevention remains the most effective weapon: it is essential to carry out correct pruning with clean and slightly inclined cuts to facilitate water flow, protect pruning wounds with healing mastics, and maintain a good vegetative state of the plant through appropriate agronomic practices. A regular monitoring program, especially after adverse weather events or pruning interventions, can help to identify early any entry points for decay pathogens.
Gummosis
Gummosis is another major disease of tree trunks, caused by a combination of causes (fungi, bacteria, stress) that lead to its main manifestation: the discharge of exudate from trunks or branches. The phenomenon, which manifests as a viscous amber- or brownish-colored secretion, represents a defensive response of the plant to stress conditions or pathogen attacks. The gum produced is a complex mixture of polysaccharides and other substances that the plant secretes in an attempt to isolate and contain the damaging agent. The condition particularly affects stone fruit trees such as peach, cherry, apricot, and plum, but it can also occur in other fruit tree species.
Given that the factors that cause exudate production are diverse, different interventions will be needed to counteract the phenomenon depending on the causes of the condition. Accurate diagnosis of the triggering cause is essential for effective treatment. Predisposing factors include unfavorable environmental conditions such as sudden temperature changes, water stress (both water shortage and excess), nutritional imbalances, particularly excess nitrogen, and mechanical trauma caused by inappropriate cultivation practices or weather events. The age of the plant and its genetic predisposition can also influence the occurrence of gummosis.
For example, if the gummosis is related to pruning cuts, it will be appropriate to disinfect the cut with copper metal, while if it is determined by the attack of insects such as mealybugs, beetles or other phytophagous pests, it will be appropriate to eradicate the infestation with specific products for each phytophage. In the case of gummosis caused by pathogenic fungi such as Cytospora spp. or Monilinia spp., an integrated approach involving both removal of the affected parts and appropriate fungicide treatments is necessary. Prevention plays a key role and includes practices such as choosing resistant varieties, adopting proper pruning techniques with disinfection of tools, maintaining a balanced nutritional status of the plant, and optimal irrigation management. It is also important to avoid injuries during cultivation operations and promptly protect any accidental injuries with healing mastics. Regular monitoring of plant health enables early detection of symptoms and intervention before the situation becomes critical.
In the case of gummosis already in an advanced stage, in addition to specific treatments for the underlying cause, it may be necessary to proceed with the surgical removal of the affected areas, followed by disinfection and protection of the wounds. Post-operative management requires particular attention to environmental conditions and cultivation practices to avoid recurrences and promote the healing process of the plant. In some cases, it may be advisable to consult a plant pathology expert for an accurate diagnosis and a personalized intervention plan.
How to Prevent Fruit Tree Trunk Diseases
As we have seen in the previous lines, once fruit tree trunk disease has spread throughout the plant, it can be very difficult to successfully remove it.
For this very reason, prevention of tree trunk disease is certainly the safest and most effective activity to avert one’s plant being put at risk of sustainability by disease.
It is therefore advisable to keep the trees in good vegetative condition, carrying out periodic checks that can promptly intercept any anomalies. Cultivation operations must be carried out with care, avoiding wounds and traumas that could become preferential vehicles for the infection of fungi and bacteria. It is also useful to carefully disinfect pruning tools and always ensure good drainage of the soil, accompanying these precautions with the implementation of preventive treatments with copper products.
In case of suspicious symptoms, it is advisable to promptly identify the disease in order to specifically and effectively identify the most appropriate treatment. As far as possible, diseased plants should be isolated and made daily protagonists of monitoring activities for the evolution of symptoms.
Given the variety of diseases that can affect the trunk of fruit trees, in order to receive an accurate diagnosis and targeted treatment, it is always advisable to consult a specialized technician, especially in the case of unclear symptoms or particularly aggressive diseases.
The importance of constantly monitoring plants and the role of Plantvoice
From the lines shared above, it is clear that the best method to prevent and effectively deal with any disease of the trunk of fruit trees is to constantly monitor the evolution of their health.
In this regard, we remind all our readers how Plantvoice provides farmers with a number of exclusive benefits and direct information on plant physiology through a unique real-time, noninvasive sap analysis.
Our as-a-service sensor technology is in fact integrated into a practical, non-invasive, phytocompatible device, introduced directly into the plant stem, thus allowing for real-time monitoring of the physiological data of the sap.
Once the data is intercepted, the sensor sends it to the cloud to an artificial intelligence software that analyzes it using customized algorithms in order to provide detailed information, as can happen in the attack of bacteria and fungi that we talked about in this article. The information thus obtained can help agricultural companies make timely decisions, useful for preserving the health of the fruit plant and increasing the qualitative yield of their crops.
Unlike other major agricultural technologies, which use meteorological or soil sensors, satellite images and drones, and which only provide data external to the plant and related to the environment that surrounds it, Plantvoice can therefore collect internal data directly and, by analyzing its physiology, allows rapid detection of anomalies in the state of health, minimizing latency compared to competing technologies. The API interface can allow integration with other software applications, thus allowing farmers to use the data collected in other applications and tools.
