The beginning of our first winter in California brought us many unpleasant surprises. it rained heavily, wetly, and a lot in November. In the morning we had to climb in the dusty ground and shake off the branches. But by this time the little almond trees were broken.
Of course, we wrote it off as very heavy rain. When all the heavy rain had stopped while cleaning up the plot, I had examined the broken part of the trunk and found that the snow had just logically finished what the fungus had started: the trunk was all rotten inside.
Here’s the story: why the trees fell and how to fix it.
WHY ARE TREE TRUNKS ROTTING?
The answer is simple: because the fungus is destroying the wood. What kind of fungus is quite specific for each type of wood, though there are some general ones. But again, the fungus is a certain stage of unhealthy wood; it cannot be the root cause. In addition, most fungi are saprophytic, meaning that they feed on organic matter that has died from tissue or excrement.
This means that bacteria should work before fungi, although they can work at the same time. This is not the underlying reason either, because bacteria and fungi do not have legs and they only get into the right place without realizing it.
Here, the carriers of pathogenic microorganisms of woody species: insect-zygomycetes play their role. There are many of them, as well as cattails, and bark beetles, and borers, which repopulate wood bacteria and fungal microorganisms when laying eggs or with their excrement.
All other insects can also be carriers of bacterial microbes – ants, for example, can carry anything on their claws!
But bugs are not the main cause either; they are always present, and trees do not necessarily rot.
Obviously, there are three main causes: external protection, i.e., damaged bark, a decline in the tree’s overall immunity, and a combination of adverse factors.
At this point, the damage to the bark must be specific. Anyone who prunes trees knows that an even, scratch-free, smooth crosscut can be made without any caulking.
It will dry out quickly in the wind and sun, blocking all input and output of pathogens, and the surrounding cambium will grow a roll of bark in a pinch. At the same time, if the cat has not had time to dry out and warm, wet weather has set in, there is a high risk of wood infection in the area where the cut was made.
This is a direct path to infestation. Here the tree can stand with strong immunity, which unfortunately is not good for deteriorating cultivated plants.
WHAT CAUSES BARK DAMAGE?
In the spring, we had a small cherry tree that did not bloom and later leafed out, so I went to inspect it closely to find out what was going on. Rot in the lower part of the trunk was visible to the naked eye. Inspection of the other trees revealed a disheartening situation: almost all of them had bark damage on the lower trunk.
Most of them had bark rolls, but some of them had visible rot. I had to treat them urgently. I later learned from the previous owner that the bark had been damaged by the trimmer cord while mowing!
I was tempted to believe that this negligent attitude toward trees was the exception rather than the rule until I saw the results of some local residents pruning their trees. Bark torn to ribbons, not completely cut, branches half-broken – I wanted to weep for such trees!
It’s no surprise that the oldest apple tree in our yard is one big hollow. Or rather three, since it has three trunks.
Mechanical damage also includes branch breakage from wind and snow loads and overloading during harvesting.
Bark cracks are also mechanical damage and are inconvenient to deal with because the structure of the damage is extremely pathogen-friendly.
Bark cracking can be caused by many factors.
- freezing. Associated with a sharp drop in temperature in early spring or warm winter, when frost strikes as the sap begin to flow. Under normal circumstances, trees are not so stupid that they are not prepared for winter and cannot remove excess sap from their trunks in the fall. In the spring, they are eager to live.
- Hot sunburn is also a nuisance in spring. The sun is very bright and for some reason, the trees have not adapted to it. When we lived in the Khabarovsk region, our apple trees were specialized shelters. Therefore, opening them in the spring without immediate whitening was a guarantee of scalding. Despite the fact that the time of removing the shelter coincides with cloudy weather, it stays in the spring for no more than two days.
- Excessive application of nitrogen: the bark cannot keep pace with the strong growth.
- In sweet cherry wood, the cells grow faster than the bark cells. Therefore, planting in wet areas and overwatering are usually forbidden and the bark is sure to crack. Other drupes are less prone to similar troubles, and for these drupes, dryness trumps moisture.
HOW IS IT TREATED?
This depends greatly on the stage of the damage. A freshly severed limb or more precisely a stump can simply be cut back with the trunk or skeletal branch.
Gnaw wounds are the most difficult to heal and should be detected as early as possible. If the gnawing is not round and has strips of live bark left, the gnaw itself should be covered with a mixture of clay and cow dung with ash (this is one of the best repair putties). If it is round and has a very destructive amnion – you will have to do grafting “bridge” to save the tree.
If the edges are brown, you’ll have to cut everything into live wood and caulk.
Same thing with old rotten woodcut it into live wood and caulk it.
Healing is a creative process. For example, one of our young cherries lost its main stem, but the lower branches extending from the main stem were still alive and quite healthy.
The main stem was cleaned up to live wood and plastered. And the healthy side, low departing branches were moved to its roots – which were filled with soil to a height of about 12inch (30cm). Now the cherry tree is healthy and bears fruit.
WHAT DOES IMMUNITY CONSIST OF?
Immunity in trees, like immunity in humans, consists of innate (genetically determined) and acquired immunity. Innate immunity, in turn, is divided into passive and active.
Passive immunity prevents the introduction of pathogens and their development in the tissues. For example, the presence of phytohormones or phenolic compounds that are toxic to pathogens.
Active – the manifestation of a protective response. For example, hypersensitive reactions are manifested by the formation of necrotic (dead) tissue at the site of pathogen penetration or the synthesis of phytoalexins with antibiotic action. That is, the tree is not standing around waiting to be protected or eaten; it is active.
Just like in humans, immunity can be stimulated by “inoculation” – a weakly localized infection. The tree engages in phagocytosis – the intracellular digestion of fungal or bacterial hyphae – and becomes immune to that pathogen. This is how acquired immunity develops.
Just like humans – the more pathogens you repel from attack, the stronger the immunity. Overfeeding can reduce immunity, as can “greenhouse” conditions.
The main part of human immunity is provided only if the gut microbiota, in plants, is soil. And the richer and more diverse the soil microbiome, the healthier the plants will be. By the way, their fruits will be healthier.