There are a number of tree diseases that are commonly found in gardens and primarily affect fruit trees. Diseases such as scab are serious fungal diseases of the apple tree and pear tree. Scab of apple and pear trees are two tree diseases, caused by different species of fungi.
To successfully combat these diseases, it is necessary to identify the symptoms of the disease and understand the life cycle of fungi.
Symptoms of scab on the trees
An apple tree is affected by Venturia inaequalis. In some areas, such as California, in the spring and early summer, when it is still cool and the humidity is high, there exist favorable conditions for development of this fungus. It affects only apple trees and does not transfer to pear trees.
The pear is affected by another fungus Venturia pirina. It leads to a decrease in fruit quantity and a visible quality loss of pears in other parts of the country. The symptoms of tree diseases are the same as in the apple tree, but this type of fungus does not cause diseases in apple trees.
An important factor in fighting these tree diseases is early detection.
What are the signs of tree disease?
At first, there are yellowish - green spots formed on the surface of the leaf. Later, the spots become brownish - olive with a velvety film. On the apple tree, the spots are visible on the top of the leaf, while on the pear tree - on the bottom. Progressive tree diseases cause leaves to fall, and fruit lesions, which casue fruit to become inedible. If the disease affects young ovaries, they fall down, causing unripe fruit to deform, and ripe fruit to crack. The rind cracks and peels off. Scab does not kill the tree, but markedly reduces the yield and deteriorates the quality of the fruit. The wet weather contributes to these tree diseases.
The life cycle of fungal pathogens
Spores coat the leaves, fallen fruit, and browse of fruit trees. In the spring, with the appearance of humidity and heat above 44,6 F, the spores become mature and disperse throughout the tree. They fall on the browse and ovary, and germinate into mycelium. The optimum condition for the emergence of the mycelium is the temperature 44,6 F to 57 F. Depending on the weather conditions, the incubation period lasts anywhere from 8 to 20 days. The process goes even faster when new spores are maturing. The repetition of this process of infection can last up to 8 generations.
One of the reasons for tree diseases such as scab is acidic soil. Sunny weather and dry air reduce the infection of trees.
What should be done to reduce the probability of tree disease in apple trees and pear trees?
Remove the fallen leaves in autumn. They can be punched.
When you branch a garden, trim the tree in the best way so that you improve ventilation.
Dig circles around the tree trunks. Add dolomite or lime flour 140g for1m ².
Mow the grass in the garden.
Use 5% urea for rapid decomposition of affected leaves.
Measures of fighting the scab
Fungicides of different types are used:
1. Fungicides that prevent spore germination and prevent the infestation of the tree.
2. Fungicides that penetrate into leaves and suppress the propagation of the pathogen. They are used 1 - 2 days after the infection.
3. If you have found the slightest infection in the trees by the tree disease (scab), and soon after if there should come rainy weather, you should use spray fungicides for at least 9 hours. Use common sulfur, copper oxychloride, 1% bordeaux mixed with chlorinated lime. Use them during a time when the trees are in full bud and in leaf.
Do not use sulfur-containing agents, when the temperature is above 62 F. Do not use the bordeaux mixture after the fruit are set.
If the weather is wet, 3 sprayings are required. The second spraying is done 10 - 14 days after the first time. Watch the fruit garden after spraying, since a relapse of the tree diseases is possible.
Many fungicides pollute the environment and affect future harvests. Therefore, make sure that their use is rational. Learn about the local rules concerning the use of fungicides, and use them in dosages recommended on the application instructions.
Among the widespread fungicides are Chlorothalonil, Captan, Thiophanate-methyl (Topsin M), Iprodione (Rovral), and Myclobutanil.
The best protection against scab is to plant fruit trees that are resistant to this disease.
For example, there are some kinds of apple trees resistant to scab. They are Easy-Gro, Enterprise, Florina, Freedom, Goldrush, Mac-free and others.
The types of pear trees resistant to scab are: Buerre Hardy, Bristol Cross, Catillac, Gorham, Jargonelle, etc.
In order to fight tree disease, usepreventive measures of agrotechnology which help reduce their prominence.