172 DISEASES OF CROP-PLANTS 



The fructifications, small white toadstools closely resembling 

 those of Marasmius Sacchari, appear in rainy weather on the 

 blackened witch-brooms while still on the tree and also after 

 they have fallen, on the indurated pods, especially small ones 

 which have dried up on the tree, and on infected cushions. 

 They have only been found on dead twigs of normal form when 

 these came from the incompletely affected buds before mentioned. 

 They have not been recorded from any other plant, living or 

 dead. Dried-up fructifications return to their natural form 

 when moistened and resume spore-formation. 



Mode of Infection. 



The witch-brooms are produced from buds infected by the 

 spores of the fungus, which, being produced in large numbers 

 from fructifications on the trees, can readily fall or be carried by 

 air-currents into situations favourable for development. The 

 pods are infected directly by way of the stomata, or indirectly 

 from infected cushions. 



The spores readily lose their vitality on drying, and it is found 

 that unshaded cacao is very much less susceptible to the disease. 



There is no knowledge of any varietal resistance, and both 

 Theobroma hicolor and T. speciosum are susceptible to infection. 

 Control. 



The recommendations for control based on the discovery of 

 Marasmius as the cause of the disease comprise the following . — 

 (i) Admission of more sun and air by pruning and by reducing 

 shade trees. (2) Repeated and frequent clearing of the trees 

 of witch-brooms and other diseased material, including infested 

 cushions, all of which must be effectively disposed of by burning 

 or burying so that the fungus cannot fruit. (3) Spraying with 

 Bordeaux mixture once or twice annually as the season of 

 growth approaches has been recommended, but is not found to 

 be necessary for satisfactory control. 



The method of cleaning up the trees by drastic cutting back 

 of the branches before spraying is more quickly effective, but 

 this advantage does not balance the loss of more than a year's 

 crop which it involves. 



MoNiLiA Pod-Rot. 



The Monilia Pod-Rot or Watery Disease has in recent years 

 become prevalent to a serious extent in some districts of Ecuador. 

 A general account of it was given by J. B. Rorer in 1918 ; no 

 technical description has yet appeared. The disease is doubtless 

 indigenous to Ecuador, where it is found on two wild Theobroma 

 species, and has not been recognised elsewhere. It is especially 

 present in localities with a large rainfall and under such con- 

 ditions may destroy almost the entire crop. In drier districts 

 much less damage is caused. 



