DISEASES OF CITRUS TREES ] 59 



young wood caused by insects or by the thorns of the 

 branches, deficient drainage in winter, and the close 

 presence of the roots of other large trees, such as the 

 walnut, the fig and the olive. Deficient irrigation in 

 a dry year is sure to be followed by an outbreak of 

 gummosis; and a clayey retentive soil, with defective 

 drainage, is a frequent cause of gummosis in young 

 trees. 



As a preventive it is advisable to plant only trees 

 budded on the Seville or bitter orange, and not to allow 

 the trees to suffer from want of water. An excess of 

 humidity or stagnant moisture in the soil or subsoil 

 should be remedied by drainage. The use of unfermented 

 stable manure should be strictly avoided, and if the 

 percentage of potash in the soil is too low, wood -ashes 

 or chloride of potassium should be distributed evenly 

 over the ground early in spring, or in autumn, at the 

 first digging or tillage, to make up for the percentage. 

 All large wounds on the trunk, the branches and the 

 roots should be painted over with tar. When a tree is 

 infected with gummosis, the diseased bark may be cut 

 off, and the dead wood scooped out. The wound should 

 then be washed out with a 5 per / solution of sulphate 

 of copper, and when dry it should be painted over with 

 tar to prevent re-infection. When a diseased branch 

 is to be dealt with, it is better to cut it oft to prevent 

 the infection from spreading to the trunk. Rotten 

 roots should be removed, the wound heavily painted 

 with tar, and the large roots close to the diseased ones, 

 though apparently healthy, should be washed with lime- 

 milk or with fresh ash-lye. Well-rotted manure and 

 wood-ashes should be applied in moderate quantity to 

 the tree in a circular ditch 60 c. m. to i metre away 

 from the trunk. If a tree is found to be infected at several 

 points upon the trunk it is useless to try to prolong 

 its life, but should be removed, the roots carefully 

 digged up, the soil changed and a young tree planted in 



