II 
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 smaragdida, 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, Conchylia vanillana, attacks 
the rudiment of the young fruit after fertilisation, and 
if it does not cause the fruit to dry up, it produces 
