At the beginning, the galls have the aspect of small, round, soft protuberances in roots and trunk, near the surface. They can be either spongy or woody and hard, depending on the amount of vascular tissue they hold. During the fall, some tumors may totally or partially rot from the outside to the center; the tumors resume their growth during the spring, and new tumor areas may appear.
Recently formed tumors are not protected by epidermis and are easily attacked by saprophytic insects and microorganisms. When the outer section of the gall decomposes, the bacterium is released on the soil, thus being propagated at great distances by irrigation water, floods and by clinging to tillage devices and plants.
In cherry crops, the bacterium also produces tumors in roots and neck. At the beginning, these tumors are small, soft, light-colored protuberances, and they may be mistaken for root primordia. The tumors grow rapidly and acquire a darker color and a woody consistency. The age of the plant at which the infection takes place is very important: if this process occurs in adult specimens, the depressive effect of the bacterium goes unnoticed. However, if it occurs in plant nurseries or during the first years of commercial plantations, the economic impact can be really significant.
In olive plants, the bacterium produces tumors in the neck of the plant and in primary roots. At the beginning of the infection, the tumors are small and round, with a smooth surface and of a light chestnut-whitish coloring. When the tumors grow bigger, the surface turns coarse and takes on a dark brown coloring. The tumors disintegrate in the fall, thus releasing bacteria. Tumor formation results in the disorganization of xylem vessels.
In blueberry, the bacterium produces tumors (galls) at the level of the neck and deformities in roots because of abnormal growth. At the beginning, the galls,which are greenish, soft and humid, raise the bark.
Plants with a great number of galls may bear chlorosis; they may weaken, stunt and even render unproductive. In Argentina, A. tumefaciens is a primary pest in blueberry crops in all productive areas.
In grapevine, the galls are visible about two to four weeks after the infection, when temperatures range between 20 and 30 ºC. Symptoms appear later when temperatures are below 15 ºC; some infections may remain dormant until the second or third growth season. The infection is hindered with temperatures over 32 ºC. As the cells of the galls increase in number and size, they press on the normal tissues that surround them, thus deforming or even tearing them.
The information contained in the system is subject to constant changes and revisions. The Bureau of Surveillance and Monitoring reserves its right to make all necessary amendments in its listings and in the contents of the data sheets whenever appropriate.
Importing countries may, if required, contact the National Directorate of Plant Protection for an official technical report on the phytosanitary status of the crops. The Directorate shall prepare such report in accordance with the information contained in this database.