882 EXPERIMENT STj^TION RECORD. 



rot, focoanut diseases, l>anana Ivaf blight, orange root grub, and several diseases of 

 cacao. 



The logwood root rot is said to be affecting the logwood trees, especially on the 

 western end of the island, causing the destruction of many specimens. The diseased 

 trees usually occur in groups, infection spreading slowly in constantly widening 

 circles. The tissues are invaded by a white fungus mycelium, which seems to first 

 attack the small rootlets, gradually spreading to the larger roots and finally to the 

 crown, when the tree dies. The fungus causing this is probably one of the Hymeno- 

 mycetes, and for the control of the disease the author recommends digging out and 

 burning the roots of dead trees, or where a considerable area is infested, clearing the 

 tract entirely (if logwood and growing some crop that is not subject to the attack of 

 this fungus. 



Notes are also given on what is termed in the trade "bastard" logwood. This is a 

 kind of logwood which contains little or no hpematoxylin, but in its place a substance 

 yielding a dull, yellowish-green dye. From various facts observed T)y the author it 

 is believed that this is probably due to some hereditary trait on the part of the 

 plant, as only certain trees j)roduce this form of wood, and they apparently are repro- 

 duced from seed. Considerable variation has been noted in specimens of logwood 

 and it is thought jirobal)le that there may be a varietal difference. 



Among the diseases of cocoanut a description is given of a bud disease in which the 

 first symptom is the dropping of the immature nuts. The head of the tree is in all 

 cases invaded by what seems to be a bacterial rot, and bacteria are believed to be 

 the cause of the trouble. It is claimed by some planters that a green-skinned variety 

 of cocoanut is less liable to this disease than others, and facts observed seem to sup- 

 port this view. A second disease is reported in which the nuts fall a few at a time, 

 the lower leaves droop and fall prematurely, and in the final stages the leaves are 

 less than half normal size and are borne at the apex of the nearly bare stem. The 

 course of this disease is always slow, but the affected trees ultimately die. In all the 

 trees examined a white scale insect was always found at the base of the petioles and 

 on the fruiting peduncles, but these insects did not seem to l)e numerous enough to 

 account for the serious effect produced on the tree. It is said that badly affected 

 trees have recovered when subjected to a firing of the dead leaves and fibers hanging 

 on the trees. The flames kill all the fruit and open flowers as well as most of the 

 exj)anded leaves, but the apical buds are not injured and new leaves and flowers 

 soon develop. The work of the cocoanut trunk borer and the trunk rot, which are 

 perhaps somewhat related, is described. 



A l)anana leaf blight, which causes the l)rowning of the vascular bundles in tlie veins 

 and midribs of the leaves and eventually the decay of the leaf, is described. The 

 infected plants are commonly stunted in growth and do not bear fruit, and there 

 seems to be evidence that the disease is contagious. It is believed to be of bacterial 

 origin and so far is confined to one locality. 



The work of the orange root grub {Privjxxles vUlaUt) is described, the grub gnawing 

 the roots and ultimately destroying the trees. 



Among the cacao diseases mentioned is a stem canker, which is i>rol)ably due to 

 some form of Nectria, as the yellow perithecia were found abundantly developed on 

 the bark. It is believed that painting the cankers and spraying the trees with Bor- 

 deaux mixture would protect the trees against this disease. A cacao pod rot, which 

 is apparently of fungus origin, is briefly mentioned. It has as yet not attracted much 

 attention, but is liable to prove destructive, particularly with certain varieties grown 

 at low altitudes. A root disease, somewhat similar to that mentioned above as affect- 

 ing the orange, is also noted. 



A root rot of cassava was observed, in whicli the plants were somewhat similarly 

 affected as the logwood trees described above. The cassava had been planted on 



