CIKCULAE NO. 126, BUEEAU OF PLANT INDUSTRY. 



made at a time when the disease was a( its height in the field. At a later j)eriod, 

 during warm weather, this cane recovered rapidly, the stand being greatly augmented 

 by new shoots. When the field was finally harvested the yield in sugar was about 20 

 per cent less than the average amount which this field could be expected to produce. 

 The loss in this case amounted to a little over a ton of sugar on each acre. As no other 



disturbing factors appeared during the growth of this 

 crop, the loss can very reasonably be ascribed en- 

 tirely to iliau. 



We have seen several cases where iliau has killed 

 all of the stools over small areas of plant cane and 

 one case where it effectually destroyed the cane 

 over an area of 15 acres. We have seen many in- 

 stances where the disease has killed from one- 

 fourth to one-half of the primary shoots in large 

 fields, our estimates for several cases being based 

 on careful counts made in various parts of the af- 

 fected areas. 



Iliau is a Hawaiian expression meaning 

 "tight skin" or "liideboimd," having 

 reference to the manner in which the leaf 

 sheaths are funnly held together around 

 the stem by the fungous mycelium. Any 

 attempt to remove the leaves is met with 

 considerable resistance. The f ung-us gains 

 an entrance into the tissue of the cane at 

 the leaf bases usually below the surface 

 of the ground and from here makes its 

 way into the leaf sheaths, working up- 

 ward and then inward. The leaves whose 

 sheaths are diseased soon die but do not 

 fall off, as they are tightly cemented to 

 the sheaths witliin. (See fig. 2.) On 

 young cane this tight case prevents the 

 shoot from elongating and thus eventu- 

 ally kills the terminal growing point. If 

 the stem or shoot outgrows the mycelium, 

 i. e., before the fungus has penetrated the 

 inner sheaths, the disease does little harm. 

 The fungus can make material progress 

 only in young and tender tissues, and 

 even if it has entered the stem its gi'owth 

 is checked by the normal hardening of 

 the tissues. The d{>ad l(>af sheaths are 



pinkish brown in color and the rind, if any growth has been made, 



is deep bluish gray. 



The imperfect form of this fungus (Melanconium) is the one most 



commonly met with on the diseasiul shoots. It ])elongs to the same 



ICii-. 12G1 



F:g. 2.— Iluui disease of sugarcane after 

 an attempt to remove the leaves. 

 (After Cobb.) 



