VANILLA 45 



continuance of the disease depends entirely on the 

 diseased dead leaves lying on the ground. 



In the Seychelles it was observed by the first 

 reporter of the disease that it was confined to a certain 

 area of flat, damp land, insufficiently drained, and during 

 his experiments Mr. Massee found that the presence of 

 an excess of moisture in the leaf favoured the develop- 

 ment of the fungus. Macfarlane, too, in describing a 

 very similar disease, observed that it was worst in rainy 

 weather and in dense shade. 



Thus overcrowding and excessive dampness in the 

 estate are things to be avoided. 



This disease has been seen in Mauritius, the Seychelles, 

 Reunion, Antigua, New Granada, and apparently the 

 same fungus in Tahiti, where also a fungus known as 

 Colletotrichum Vanillae has been met with attacking 

 the foliage. Calospora Vanillae has also been seen 

 attacking other orchids, viz. Oncidiums and Dendrobiums 

 at Kew. 



INSECT PESTS 



These are comparatively few. The most destructive 

 one recorded is a bug, Trioza Litseae (Hemiptera, 

 Psyllidae) recorded from Reunion. It seems first to 

 have attacked an introduced tree, Litsea laurifolia, 

 and later attacked the vanilla. It attacked the buds 

 and flowers of the plants, puncturing them and pro- 

 ducing spots of decay. When it attacked the column 

 no fruit was produced. 



Another bug (Heteroptera), known as the emerald 

 bug, Nezara smaragdula, a small grass-green insect 

 occurring all over the world, lays its eggs on the leaves 

 and stalks of the vanilla, and the insects when hatched 

 suck the sap of the stalks and flower-buds. It is not 

 as destructive as the previous insect. 



A moth caterpillar, Gonchylia vanillana, attacks 

 the rudiment of the young fruit after fertilisation, and 

 if it does not cause the fruit to dry up, it produces 



