Jan. 1908.] 19 Plant Sanitation. 



A Coconut Palm Root Disease. 



The following is a report on a root disease of coconut palms reported from 

 Trinidad, West Indies :— 



Root Disease. — An attack of this disease is generally first shown by the 

 leaves. They show a slightly wilted appearance, they turn yellow, first at the tips 

 and then gradually all over the leaflets. These dry up, blacken, hang down from 

 the ' cabbage,' and often remain for a considerable time before they are shed, — a 

 badly attacked palm often being entirely enclosed in numbers of leaves around its 

 trunk. Frequently, however, it is noticed that the leaves do not hang down around 

 the trunk but the petioles break across, leaving the sheathing portion on the trunk, 

 while the foliage portions of the leaves have fallen to the ground. Sometimes the 

 petiole does not completely break and the foliage portion of the leaves hangs 

 vertically downwards, attached to the portion of the petiole that is left attached to 

 the stem. 



The outer leaves are sometimes those that show signs of wilting and yellow- 

 ing first, but this is not always so, for frequently palms may be noticed in which a 

 'middle 'ring of leaves becomes wilted and yellow, while rings of green leaves 

 remain above and below. 



After the yellowing of the leaves, trees bearing a good crop of nuts as a rule 

 gradually shed most if not all of them, irrespective of their size and state of develop* 

 ment, and the flowers subsequently produced do not set. In fact, it is possible for a 

 person to pick out with certainty trees that are diseased before any yellowing of the 

 leaves is noticed, by carefully looking at the condition of the leavees and at 

 the latest flowers that are being put forward. Any trees that are diseased can 

 at once be singled out. The local conditions of the soil must be considered before a 

 tree is definitely stated to be diseased, as the whole appearance of the diseased 

 trees suggests a lack of water, and therefore may be confused with trees that are 

 suffering from this cause alone in drought-affected areas. 



An increased supply of water, either natural or artificial, will improve the 

 condition of drought-affected trees, but the wilted appearance of diseased trees, 

 albhough it may be slightly less noticeable, is more permanent, and the symptoms 

 do not disappear. 



After a number of the leaves have yellowed and died, it is only a question of 

 time before the terminal bud falls over and becomes a putrid mass,* and the palm 

 eventually dies, as it has no power of branching or of producing a new growing 

 point. 



Trees which only present external signs of disease to the experienced observer 

 show that apparently the roots are probably the parts which become first affected. 

 j±f ter a considerable number of these have been rendered useless in contributing to 

 the life of the plant, changes take place which result in a sour-smelling red dis- 

 colouration in the stem that probably commences at the level of the ground and 

 extends upwards. 



The position of this red discolouration would appear to vary in the stem 

 directly with the roots that are affected, and it has been repeatedly noticed that 

 when a ' middle ' ring of leaves shows signs of yellowing, the discolouration is found 

 towards the centre, while if the lowest leaves become wilted, the stem presents a 

 ring of discolouration towards the outside of the stem. The petioles also show that 



* When a coconut palm is affected by any disease or pest, the terminal bud, in the 

 advanced stages, becomes involved in a rot. This must not be confused with ' bud-rot ' which 

 appears to be a specific disease, as the roots, stem and leaves are sound, while the bud is in a 

 diseased condition. 



