It is a serious disease that affects citrus trees, especially in Lower Egypt and Fayoum, and causes very large losses in citrus farms, especially in farms grafted on orange rootstock, or in which the graft area is close to the surface of the soil, or citrus fruits grown in heavy clay lands.

 The cause is called the fungus

 Phytophthora citrophthora

 Suitable conditions for the spread of disease, gum disease in citrus fruits

low temperature

 Increase in air humidity

 Cracks or wounds occur in the bark of trees, whether in the main branches, sub-branches, or fruits

 Use of Not resistant to injury

 Direct contact of water with tree roots

Description of fungi

 The row of oocysts is followed by the mycelium, which is undivided, and the hyphae carry oval or lemon-shaped germ sacs resembling lemon dahlias, at the top of which there is a nipple. When the ciliate spores emerge, during the germination of the germ sacs, the ciliated spores move quickly, and their ciliates disappear after a period of germination, and then an infection occurs to the host, this fungus.

 Sexual reproduction of this fungus has not been observed yet, but asexual reproduction occurs only in the soil

Symptoms of infection: Symptoms appear in two cases

•  The first case is that the symptoms of infection below the soil surface turn the color of the outer layers of the bark into black
•  Occurrence of infection with secondary parasites that cause discoloration of wood tissue and may cause death of these tissues
•  It causes dry rot of the primary and secondary roots
•  Symptoms of infection on the surface of the soil: Secretion of a very large amount of glue in the area of the infection in the inner bark
•  Longitudinal cracking and drying along the bark of the tree trunk
•  Rot occurs at the base of the stem
•  Symptoms spread from the bottom of the soil surface to the top when the infection is severe
•  Symptoms appear on fruits in the 
• form of brown spots

 Integrated control of gum fungus

•  It is preferable that the vaccination area be above the soil surface, at a height of 30 to 50 cm above the soil surface
•  Cultivation of resistant varieties such as orange
•  Paint the tree trunk from the surface of the soil to a height of 40 cm using Bordeaux paste periodically.
•  Avoid placing irrigation water directly and adjacent to tree trunks, as well as organic fertilizers
•  It is preferable that irrigation be done in a circle system around the tree trunks to prevent water from reaching the tree trunks directly
•  Or it is preferable for irrigation with a terrace system
•  Getting rid of the infected bark by removing it, as well as removing part of the healthy bark, using a sharp knife in the affected area.
•  During the process of scraping and eradicating the affected areas, the cambial area must not be reached and disinfected with a solution of potassium permanganate (one suspension/liter of water), and upon healing, it is covered with putamen or any non-toxic paints.
•  Add copper sulphate to irrigation water at a rate of 20% ppm and continue adding it for one year of cultivation.
•  Bordeaux paste is sprayed in November and December after rainfall
•  We may have to repeat the spraying in January and February in the case of severe infestations
•  It must be planted in clean lands that are not contaminated with fungal spores, or the soil must be disinfected with 30% fabane.
•  The farm is left for a month and then planted to improve the drainage process in these lands
•  Digging long tunnels and canals near trees to drain excess water. It is preferable to rationalize irrigation and give the plant an appropriate amount without exceeding its need.