Peach leaves curl

Apricot diseases

The scientific name : peach leaf curl
The causative fungus : Taphrina sp
Symptoms of the disease :
Symptoms appear in the form of deformities in the leaves, where dents appear on the upper surface of parts of the leaf or on the entire leaf, and they become thick and curled downward and inward, and a group of hollow wrinkles appear on the lower surface. Infected leaves appear reddish or crimson at first, and later when galls form on their upper surface, they become fine gray in appearance, then turn yellow or brown and fall... Flowers, young fruits, and newly formed parcels may also be infected. Infected flowers and fruits usually fall early during the season. Infected parcels appear swollen and stunted, and usually die during the summer.

The causes of disease :
Fungi that cause leaves to curl
The causative fungus prefers humid weather that lasts for at least 12.5 hours. (Two days of humid weather is best) The temperature should be below 61°F but above 47°F... When the temperature reaches 69°F, division stops.
Lack of attention to agricultural operations, such as pruning, balanced fertilization, and irrigation
Failure to remove plant waste from the field.

Low temperature and high humidity encourage infection.
The infection infects new leaves and is transmitted to other tree parts by rain and wind

The fungus spends the winter in the form of ascospores or bud spores on the surface of the bark, most likely between the scales of dormant buds. In the fall, when the weather becomes cold and humid, especially when it rains, the ascospores germinate to give bud spores.
In the spring, as the new leaves begin to appear, the old bud spores that have spent the winter and the newly formed ones are spread by rain spray, to germinate and infect the leaves and other newly formed plant organs, directly through the peel or through the pores.
The fungus mycelium grows between the cells, inciting them to randomly divide and grow in excess of normal, which leads to the affected organs becoming enlarged and deformed.
Red plant pigments also accumulate in the deformed cells, giving the affected tissue a red color. Then the fungal mycelium grows between the scale and the epidermis, forming spores that put pressure on the scale from below, and then emerge in the form of a layer of pedunculated spores, which gives the surface of the affected tissue a delicate, gray appearance.
Ascospores are thrown into the air, carried by the wind to plant tissues, and bud to give bud conidia. The infection usually occurs shortly after the buds open. As plant organs age, they become more resistant to disease

Tree vigor, fruit quality and productivity decrease.
If significant leaf drop occurs prematurely, trees will be susceptible to drought stress and winter injury

Planting resistant varieties.
Proper pruning in the fall.
Do not water the tree with overhead sprinklers as this may spread the spores.
Remove all infected leaves and plant parts from trees and dispose of them.
Remove all fallen leaves in the field and dispose of them immediately.
Do not place infected leaves or parts on top of fertilizers or in the field.
Placing a protective canopy over the trees in early January to late April to protect them from rain and dew, which contributes to significantly reducing infection.

Chemical and organic control recommendations
Organic control: Immediate removal of infected leaves before white spores appear will help reduce the amount of fungi transmitted to the following year
Fungicide in the fall after leaves fall.
Chemical control: Spraying Silite on wet leaves at low temperatures, using Silite at a rate of 100-150 mm/100 liters of water.
It is best to carry out a spraying at the end of autumn after the leaves have fallen, and in areas where humid weather and heavy rain prevail during the winter... A second spraying can be carried out at the beginning of spring before the flower buds begin to swell... Among the pesticides used are: Bordeaux mixture of boiled lime and sulfur, oxychlor. Copper, chlorthalonil, trifurin, and captan.

-, Singh, AK, Singh, AP, Singh, AK, & Sharma, AK Managing leaf curl for quality peach production. Indian Horticulture, 56(1).

Cissé, O. H., Almeida, J. M., Fonseca, Á., Kumar, A. A., Salojärvi, J., Overmyer, K., … & Pagni, M. (2013). Genome sequencing of the plant pathogen Taphrina deformans, the causal agent of peach leaf curl. Mbio, 4(3), 10-1128

Pierce, N. B. (1900). Peach leaf curl: its nature and treatment (No. 20). US Government Printing Office

Links:

Peach leaf curl

https://www.rhs.org.uk/disease/peach-leaf-curl

https://books.google.com/books?hl=ar&lr=&id=tLdGAQAAIAAJ&oi=fnd&pg=PA11&dq=peach+leaf+curl&ots=ieaGGLdA5i&sig=BwTkAwPOMX_nWGNt8C9WUuom0Zo