TOP-ROT OF SUGAR-CANE IN JAVA. 



In my account of the disease I follow Wakker. 



For the first time in the year 1895 in Java attention was more particularly given to the 

 top-rot, a disease which previously was to be found sporadically but had now begun to be 

 epidemic. 



Following Cobb, it was first named gum disease, but since the signs do not entirely 

 accord with the ones given by him, Wakker prefers to use the above name, even though the 

 diseases in Java and in Australia should prove to be identical, especially because the name 

 "gum disease" is not happily chosen, gum formation occurring in nearly all diseases of the 

 cane, and even in connection with a wound. 



The disease has been observed in Java in a dangerous form, especially on the Loethers 

 or Louzier cane (mostly in West Java), and on the striped Preanger cane (more particularly 

 in East Java), and to a less degree also on Cheribon cane. 



The signs appear chiefly in the beginning of the rainy season ; later no other cases occur, 

 and during the dry period of the east monsoon one does not usually notice any signs of the 

 disease. 



It is highly probable that the so-called heart-disease, and that known as Pokkah-bong, 

 have the same cause as the top-rot. 



The following are the signs of the three diseases mentioned by Wakker : 



A. The top-rot in stricter sense. 



Externally the signs accord wholly with those caused by the top borer : the youngest leaves are 

 black and decayed at the base and more or less dried up at the top. Soon the older leaves also dry up. 



The younger leaves can be pulled out without any trouble, and it is then that an almost unbear- 

 able odor is first noticed. If the affected tops are cut through lengthwise, one notices in the typical 

 far advanced cases that the younger leaf-sheaths are brown and dead, while the youngest leaves are 

 changed into a feeble, twisted (wormvormige) mass. 



The growing-point is either normal or changed to a yellowish-white slime (brei), while the rest of 

 the young stem-top has become, on the inside to a greater or less extent, a glassy mass, which is sepa- 

 rated from the outside by a clear red line. This outside is as good as unchanged. 



Usually in the youngest part of the top there also appear cavities, which are much broader than 

 high, and on a lengthwise section look like cross-cracks. 



bater the glassy tissue disappears more or less, and then large lengthwise cavities appear, in 

 which the vessel bundles are to be found as white threads almost unchanged. 



Generally the disorganization does not go much farther than the growing articulations. A few 

 times, however, Wakker found plants a couple of meters high which were wholly affected by the top- 

 rot and killed. Down to the underground stem-piece the central tissue was glassy and surrounded 

 by a red line. 



If the signs are confined to the top, the buds under the diseased spot sprout, as in all other cases 

 in which the growing-point is destroyed or ceases to grow. Such sprouting buds do not usually get 

 the disease. In genuine cases of top-rot larvae are never found. If the growing-point remains sound, 

 while the leaf-sheaths have already died, or at least have been affected, combined or not with dis- 

 eased spots in the stem under the growing-point, and, if in such plants the top-rot does not go farther, 

 then the stems may grow on, never, however, without later showing the consequences in the joints 

 becoming crooked or remaining short, which then dry up more or less. 



B. The Heart Disease. 



Till now this disease is known to exist only in a few mountain bibit plantations. According to 

 Went it is nothing else than a special case of top-rot in young plants. Externally one sees the young 

 leaves curl up, take on a yellow-gray tint, and decay. In a lengthwise section it is seen that in the 

 heart of the plant the youngest leaves, sometimes also the stem-top, have to a certain extent colored 

 brown and died, showing for the most part cross-wrinkles. 



C. The Pokkah-bong or chlorosis of the central leaves. 



Under the Javanese name of Pokkah-bong (broken sprout) some signs are grouped which until 

 lately seemed to have little practical interest, but which are not wholly without significance. 



