252 DISEASES OF CROP-PLANTS 



not been found on the sickly leaves resulting from disease of more 

 remote parts of the plant. 



Associated Fungus. 



The fungus is described as a new species by Ashby under the 

 name Cercospora musarum. The conidiophores appear mainly 

 on the under side of the leaf. They are septate, simple or once 

 branched, and often elbowed. They terminate in an inflated 

 head bearing one conidium, and may continue to grow producing 

 a succession of such heads. The conidia are smoky olive in 

 colour, pear-shaped, widest above the base, and narrowing 

 thence to a blunt point ; the base shows a dark pad or disc 

 marking the point of attachment ; they are thick-walled with thick 

 septa, occurring as long forms with 6-q cells of average dimen- 

 sions 50-60 X 16-17 microns, and stumpy forms with 4-5 cells, 

 similar in breadth and not exceeding 30-40 microns in length. 



Should treatment become necessary the indications are that 

 it would be best effected by spraying with Bordeaux mixture 

 at an early stage. 



BONNYGATE DISEASE. 



The Bonnygate disease, named from the place of its discovery, 

 has been found at several scattered points in Jamaica. It is 

 attributed to the infestation of the rootstock with a fungus 

 described as a new species by Ashby under the name Sphcerostilbe 

 musarum. 



Symptoms. 



The leaves show a narrow zone of pale brown dry tissue 

 extending along the margin of the blade, bordered on the inner 

 side by a narrow but sharply defined bright yellow band. This 

 appears on one or several among the older and outer leaves. 

 The younger inner leaves usually bear broader dry and yellow 

 bands. This condition may continue stationary for weeks, 

 the rest of the blade remaining green. Suckers are backward 

 in growth and if they produce a bunch it often fails to reach 

 full size. The lower part of the trunk often turns black for a 

 few inches above the base and the plants may be broken across 

 at the bulb by a moderate breeze. 



In the cortical region of the rootstock occur rounded water- 

 soaked areas bounded by a narrow red line. In parts where the 

 affection is more advanced the tissue may be discoloured in dark 

 brown bands which enclose the root-like strands, black without 

 and white within, of the causative fungus. 



Causative Fungus. 



As in other Sphasrostilbe diseases the fungus produces broad 

 flat branching rhizomorphs, which give rise to the strands 



