Apple tree problems: the expert answers on apple tree diseases

Apple tree problems: the expert answers on apple tree diseases



Malus domestica(Family Rosaceae)

The section is dedicated to plant problems.If you wish to write to our agronomist in order to have an answer on an unclear situation or a difficulty concerning your plant, it is necessary that you indicate:

  1. what plant it is;
  2. where it is located (inside the house, on the terrace, in the garden, etc.);
  3. the type of exposure (full sun, half-light, etc.);
  4. how long has it been in your possession;
  5. the general state of the plant;
  6. the frequency of watering;
  7. how often it is fertilized and the type of fertilizer used;
  8. any pesticide treatments carried out;
  9. the symptoms it presents and the parts of the plant affect;
  10. any foreign presence (insects or other).

If possible, send a photo, but in any case, take care to be very detailed in describing the overall state of the plant. The address to which everything is forwarded is: [email protected]

Your questions

Apple tree, the lenticellar rot is there but you can't see it

From the field to the post harvest, the apple tree is exposed to pathogens such as Gloeosporium spp., Penicillium spp., Alternaria spp. is Botrytis cinerea able to damage the fruit even in the storage phase, causing serious production losses. For this reason, the defense of the apple tree must control not only the main diseases present in the field, such as scab, powdery mildew, alternaria and anthracnose, but also contain the secondary ones that emerge in the post-harvest. Among these, the lenticellar rot caused by the saprophytic fungus Phlyctema vagabunda (formerly Gloeosporium album).

Without mancozeb and with captan and dithianon contingent

In particular, Dalpiaz underlines, in the presence of several dossiers under discussion to accelerate the revision process of some active substances essential for defense strategies in the integrated production of European apple growing, where there is the danger of a possible withdrawal or at least strong reductions we tried to understand what actions to take.

Let's not forget underlines the director, that the sector already suffers the lack of renewal for the s.a. “Mancozeb” and now, with possible restrictions for the “captan” and for the dithianon ”, the pillars themselves in the integrated defense of the apple tree could be compromised. The impossibility of using these active substances that producers outside the EU regularly use, in addition to the growing supply of apples in Europe, but also in neighboring countries, represent a very real threat to EU apple growing, which would risk losing competitiveness and consequently market shares.

Pruning is the extra weapon against the powdery mildew of the apple tree

Powdery mildew or bad white represents an important fungal adversity for the apple tree, second only to scab for danger.

It is an active mushroom from the early vegetative stages because it is able to overwinter on the apple tree like mycelium on the buds.

The causative agent of the disease is the fungus Podosphaera leucotricha, which completes its life cycle in the agamic form of Oidium farinosum.

The wintering mycelium in the buds starts the primary infection very early, causing the disease to appear on the first shoots as soon as they develop, while subsequent secondary infections during the spring-summer months are produced by the conidia of the agamic form.

The disease can affect the apple tree in all its organs, but it shows particular virulence on the young shoots that show a stunted growth and various deformations accompanied by the presence of the classic whitish and floury mold, the affected organs undergo an irreversible necrosis. On the leaves the flap appears deformed and covered by an abundant mold, while on the fruits, attacked more rarely, rusty areas are highlighted, as well as a reduced growth.

Varietal sensitivity

Among the factors that favor the spread of the disease, an accentuated sensitivity of some cultivars over others plays a leading role. Just as the cultivars of the Red Delicious group are not very receptive, there are cultivars particularly predisposed to being attacked by powdery mildew: Jonathan, Jona Gold, Imperatore, Golden Delicious, Summered Rome Beaty and Granny Smith.

Another important element that can favor the development of the disease is represented by excessive nitrogen fertilizations, which favor an excessive vegetative growth of the plants with the presence of numerous young shoots in rapid growth, a substrate preferred by the fungus for its development.

The spread of the disease is closely correlated with the climatic trend. In particular, it should be remembered the particularity of powdery mildew of being favored in spreading by windy days rather than by a humid and rainy seasonal trend, as the germination of conidia is hindered by the presence of water, while the wind favors its dispersion.

The protection of the apple tree from powdery mildew first of all passes through some basic agronomic practices to reduce the potential for inoculation.

The wintering inoculum

First of all, it is necessary to eliminate the carrying buds of the wintering mycelium during the winter pruning and secondly it is a question of eliminating the affected shoots in the spring / summer.

The buds affected by powdery mildew, especially the apical ones, take on a different appearance from that of healthy buds, resulting in smaller and more pointed.

Numerous crop protection products are available in integrated production, starting with the classic and always valid sulfur, with different mechanisms of action for specific treatments to be carried out up to the pre-flowering on particularly sensitive cultivars and in areas where infections occur most frequently. These first interventions take on the value of preventive interventions which are then followed up with a targeted strategy. In other cases it is possible to start the chemical defense when the first symptoms are found.

The formulations available

In the 2015 Integrated Production specification of the Emilia Romagna region it is allowed to use the following active substances against the powdery mildew of the apple tree:

- I.B.E. (cyproconazole, penconazole, fenbuconazole, tetraconazole, difenconazole) with a maximum of 4 interventions per year

- trifloxystrobin (maximum 3 surgeries per year)

- pyraclostrobin alone or mixed with boscalid (maximum 3 interventions per year)

- quinoxifen (maximum 3 interventions per year)

- cyflufenamide (maximum 2 surgeries per year)

- tebuconazole + fluopyram (maximum 2 surgeries per year).

To prevent and limit the problems caused by the resistance of pathogens to fungicides, it is recommended to alternate active substances with different mechanisms of action

It should be emphasized that generally in apple orchards where the agronomic practices of eliminating infected buds during pruning and the first attacked vegetative buds have been applied, which fall within the defense schemes of integrated production, the disease rarely appears, also because in any case contained by the treatments carried out for the control of scab able to protect the vegetation also from powdery mildew.

The condition of apple orchards under organic farming is different, where the problem takes on a very different value and preventive defense treatments are based on the use of sulfur in these conditions, winter cleaning and the first shoots attacked by the disease become even more important.

As for sulfur, it is necessary to use it with decreasing doses as the temperature increases, as it can be phytotoxic and, therefore, it is recommended to use it in the cooler hours of the day.

It is also important to choose apple varieties less sensitive to powdery mildew for new plants, especially in areas of greatest risk.

In summer, the disease generally, with rising temperatures and a relative lower receptivity of the plant, loses danger also because it finds its upper thermal limit in 33 ° C.

* Agriculture and Environment Center “G. Nicoli "

Between misery and epidemic, what future?

The dreaded Covid wave in the autumn has arrived and fears are growing for the health system's stability but also, and perhaps even more so, for the consequences that a new contraction can cause on an economy already in great difficulty. The crisis caused by the Coronavirus has produced the largest increase in the debt-to-GDP ratio in the Eurozone in Italy. According to the calculations of the Conte government, at the end of the year the debt will be a 2,470.3 billion, that is 194 billion above the stock of 2019. And at the end of 2023 the increase compared to last year will be 503 billion.

This is the combined effect of a fall in the economy and a surge in net debt that recorded the record increase in debt / GDP from Covid in Italy, which is the most important indicator for measuring the prospects for public finances. The +23.4 that separates 134.6% at the end of 2019 from the 158% indicated for this year slightly exceeds (one decimal) the increase (+23,3) from Spain (which in any case brings the Spanish debt to 118.8%). The rise in debt is also intense in Greece (+20,8) and France (+19,4). Germany indicates a +11.4.

The 100 billion that gave resources to the three anti-crisis decrees of March, May and August are one of the engines of the large Italian debt. The rest comes from the fall in revenues, which stop at 56.2 billion below the levels of 2019.

To prevent the absolute value of debt from becoming too serious a problem to manage, growth is needed, but businesses and jobs are needed for growth.

Businesses and work that need entrepreneurs who can operate in certain times and with serious rules as well as safe with a new approach to work and businesses by the public sector. In short, we need services and an intelligent and not obtuse bureaucracy that leaves space and breath for the opportunities that arise and resist even in this phase of great suffering for the whole community.

2020 ("An bisest an ..." as "the Apple tree”Had headlined the issue of last January) in a while it will finally be behind us with all the troubles it has brought us but with the cold season the questions increase for 2021, the year (perhaps) of the vaccine but not for everyone and who knows when! Meanwhile, the daily hammering on TV, newspapers and social networks on the progress of the pandemic continues and consequently the concern that risks leading to fear or even terror about the future grows. But is it really so? Compared to the first wave, hospitals and doctors are now more experienced and effective on treatments and this is demonstrated by the number of hospitalizations in intensive care and even deaths register numbers that are not even comparable, so far, with last spring.

On the other hand, the freezing of treatments and the postponement of treatments for the many other diseases that have not disappeared as it seems from the health bulletins that speak only of Covid are worrying.

And the fate of those who, not protected and guaranteed by a fixed salary or a pension, have to earn the survival of their family day by day through work alarms. And there are not a few!

This does not mean letting your guard down because the curve can always grow, putting the most fragile people at risk. Rather it serves to make it clear that it would take little to contain the epidemic if everyone scrupulously followed the precautions and recommended behaviors (and now also imposed) by the health authorities.

There is no valid cure

No.There are no effective treatment systems for plants affected by fire blight and any suspected cases in vain reported to official bodies competent, such as i Regional Phytosanitary Services, in order to have a certain diagnosis and to avoid, by adopting control methods, the rapid spread of the disease.
The severely affected plants, as well as the infected parts removed, must be burned and not reused, for example in compost. On plants with modest and lmimicked foci of infection, it is possible to carry out treatments with products based on copper, to be distributed on the vegetation starting from the end of winter, or at the vegetative restart, between the enlargement of the buds and the pre-flowering. Copper has only one bland control effect on the bacteria of the shot of fire and on fruit trees should not be distributed during flowering, because it can ruin the flowers, while it can be distributed again when the fruits have started to swell and also later in autumn, when the plants are now in the resting phase.

Rootstocks, the solution to many problems

The practice of grafting to improve the characteristics of production has been known since time immemorial, the goal is to obtain a new plant that combines the best characteristics of the two starting elements. The starting plants must be different but compatible with each other.
In recent years the practice has also become of great interest in the horticultural sector, the grafting of some species has become a growing nursery technique with ample room for improvement, both in the use of cultivation techniques, in the nursery and in cultivation, and in choosing the most appropriate rootstocks.
From a perspective of evolution in the improvement of cultivation systems it becomes essential to choose the rootstock correctly, since the agronomic management of the grafted plant can change according to its physiology and the bio-resistances that distinguish it.
The beginning
The initial reason that prompted farmers to use grafted plants was the resistance of rootstocks to some telluric pathogens, indirectly favored in their spread by the intense use of fumigation with methyl bromide. It should be emphasized that the adoption of the herbaceous graft allows not only to exploit the beneficial effects related to the tolerance of the rootstock to diseases and parasites, but also favors the exploitation of the great vigor of the grafted plants.
Over the last few years, the use of grafted plants has become increasingly common in many countries for important crops: tomato (Solanum lycopersicum), aubergine (Solanum melongena), pepper (Capsicum annuum), melon (Cucumis melo) ), cucumber (Cucumis sativus), watermelon (Citrullus lanatus) and pumpkin (Cucurbita maxima). The spread took place in these areas mainly to obtain resistance to terrestrial diseases and tolerance to abiotic stresses such as salinity, in humid soils, at high and low temperatures to improve the absorption efficiency of water and nutrients, extend the duration of the harvest period and improve fruit quality.
Grafting is basically the union of two or more parts of the plant with various techniques that manage to develop a single plant. The use of grafted seedlings has become an increasingly widespread practice in many parts of the world, especially in the Mediterranean, where the use of agricultural land is very intense, this practice is considered an innovative technique and is increasingly in demand by farmers.
Ground problems
Due to the limited availability of arable land and intensive agriculture, which tends to reduce crop rotations, plants are often grown in unfavorable conditions that induce stress. These conditions include environments that are too cold, humid, dry, lacking in oxygen, saline, contaminated with heavy metals, with an excessive or insufficient availability of nutrients or with an unfavorable pH. These conditions cause various physiological and pathological problems, which result in yield losses.
The use of grafted seedlings is a strategic tool for solving these problems
This technique is spreading more and more, especially on plants belonging to the Solanaceae and Cucurbitaceae families.
The phenomenon of soil fatigue (presence of pathogens and loss of fertility) has become an increasingly serious problem in the cultivation of numerous species grafting has progressively become the most common and effective method for the control of terrestrial diseases, such as Phytophthora spp and Meloidogyne spp.
The choice
The choice of rootstock thus becomes a key element in solving specific business problems because each species has specific characteristics in terms of vigor, tolerance to salinity and resistance to soil diseases or parasites. All these characteristics must be accompanied by a perfect compatibility between the rootstock and the variety.
The graft has been widely used in the production of tomatoes, in order to reduce damage from soil pathogens and, more recently, it has been used to induce resistance to low and high temperatures, to iron chlorosis in calcareous soils, to improve the absorption of nutrients, to increase the synthesis of endogenous hormones and to optimize the use of water. Previously, it was shown that rootstock can also increase the tolerance to salinity in tomatoes, assessed on the basis of fruit yield. Consequently, grafting can be considered a useful tool for growers to increase the quality and quantity of products.
Rootstocks, in general, have a more vigorous root system, this implies a greater and better exploitation of water and minerals.
In addition, improvements in color, shape, berry texture, and concentration of soluble solids in the fruit can be incorporated into the variety to be grown.
However, each of these benefits depends on the right graft – rootstock combination.
The selectors
The seed companies producing and selecting rootstocks specify for each type of rootstock the characteristics that emerged during genetic selection with particular reference to: level of resistance to diseases (eg. Fusarium spp), plant habit and vegetative development, influence on the crop cycle and productivity.
The optimal management conditions of the nursery are then indicated, especially with respect to the emergency, the required temperatures and the overall development of the rootstock with indications on sowing it with respect to the sowing of the graft so as to obtain the two elements ready simultaneously at the right level of development.
In the catalogs, a profile of the characteristics of the new plant obtained and the optimal cultivation conditions are then traced to make the most of its characteristics.
The final goal is to achieve a higher yield and a higher quality of the final product, which translates into a higher profit.

Video: Organic pest control: Apple trees Aphids Scab Mildew u0026 fungi. Gardening u0026 allotment fruit tree care.