54 [ DISEASES OF CITRUS TREES 



chlorophyll are more or less subject. In Citrus trees, 

 the disease may be due to a state of malnutrition brought 

 about by defective physical or chemical qualities of the 

 soil and subsoil, or to a faulty situation, or to stagnant 

 moisture in the soil or to the loss of foliage in winter. 

 The foliage assumes a yellowish sickly hue, the young 

 twigs are thin, small, sickly and poorly clad with leaves, 

 which are small and undeveloped, and soon dry up and 

 fall off. The upper branches begin to die off, and then 

 the larger ones, and after an attempt at revival which is 

 manifested by the formation of a number of sickly shoots 

 on the trunk, the tree dies a lingering death. The 

 disease generally takes from one to five years to run its 

 course. Young trees recently transplanted succumb more 

 rapidly, but adult trees are liable to the disease only 

 when some new factor supervenes to alter the former 

 status. In its first stages the disease is easily cured by 

 good treatment, and by the early removal of the adverse 

 factor. Trees which have been severely affected by bad 

 weather often show well marked signs of incipient 

 chlorosis in the spring, the first symptom consisting in 

 an over-production of blossoms unaccompanied by 

 foliage (anthomania) , soon afterwards followed by the 

 characteristic small chlorotic twigs, but usually recover 

 with good cultivation. Recovery is difficult or improbable 

 when the disease has been allowed to remain long, and 

 when big branches have already died off. 



2. SUNSTROKE OR SUNBURN. (M.==//^/0). This is 

 often a disease of considerable gravity, and may make 

 its appearance at any time from May to December. It 

 may start very insidiously and much injury may be 

 caused in a very short time. The disease may be caused 

 directly by the sultry and dry winds blowing from the 

 S.R., S., or S.W., or by a sudden change to W. or 

 N.W., after a prolonged spell of calm and hot 

 weather. In both cases the cause is the same, namely the 

 break of equilibrium between the absorbing power of 



