49 



of the bud is reached, it also is destroyed, and the whole head 

 withers and falls off. Not alone, therefore, is the crop lost, but the 

 whole tree is killed, the damage caused in the affected districts 

 being very heavy. 



In the diseased spots on the leaf sheaths and also on the wither- 

 ed fruit stalks, a fungus of the genns Phytophthora is found. There 

 is little doubt that this is the cause of the disease. The few 

 species of PhytoptJwra are all virulent parasites, and though the 

 well-known Phytophthora infcslans, the cause of the potato disease, 

 has been grown on dead substances, its development is much less 

 vigorous than on its living host. The betel palm Phytophthora is 

 evidently, from its position, anatomical characters and the enor- 

 mous quantity of spores which it produces, an active parasite. 



The fungus consists of a mycelium or vegetative part living 

 within the tissues of the palm and extending out on to the surface, 

 and of sporangia or reproductive bodies formed exclusively on the 

 external filaments of the mycelium. The internal part consists of 

 colourless threads lying between the cells. Here and there these 

 filaments reach to the surface and grow out into short branched 

 threads. At the ends of these, and also sometimes on short stalks 

 set laterally, the sporangia are produced. They are pear-shaped 

 bodies with the broad end attached to the stalk, from which they 

 fall easily. In water they germinate rapidly, giving rise each to 

 a dozen or more tiny swimming spores, the zoospores. These 

 swim off in all directions and after a time come to rest, get quite 

 round and in their turn germinate by putting out a thread. It is 

 by means of these sporangia and zoospores that the disease is 

 propagated. 



Since for their proper germination Phytophthora sporangia re- 

 quire to fall into water, most if not all the diseases due to these 

 fungi are closely dependent on conditions of moisture and 

 rainfall. For the spread of the betel-nut disease which appear to 

 begin on the flower and fruit stalks, it is necessary that the mois- 

 ture conditions should be favourable during the time of setting of 

 the fruit. The heavy monsoon rains in these parts of Mysore 

 begin in June and last until the end of August or September. 

 The following observations may serve to explain the increase in 

 severity of the disease in recent years, and also its restriction to a 

 single area. 



"When the disease first made its appearance, some thirty or 

 forty years ago, it was customary to harvest the nuts in November 

 or December. For the last twenty years the harvest has become 

 earlier, being sometimes collected as soon as July or August. 

 This indicates a change in the habit of the tree, due either to a 

 different method of treatment or the introduction of an earlier 

 variety. The effect of this is to expose the fruit stalks to 

 infection at a time when the moisture conditions are most favour- 

 able for its growth. In some gardens the harvest is still gathered 

 in December, and in these I was informed that there is little 

 complaint of loss from the disease. In Mudigere and adjoining 

 parts of Mysore the harvest is ordinarily in December and 



