THE SUGAR-CANE LEAFHOPPER. 19 
the presence of the pineapple disease of sugar cane (Thielaviopsis 
ethaceticus) and the rind disease (Melanconium sacchari). The latter 
species, it is believed, gains entrance to the tissue of the plant through 
the wounds made by the leafhopper. 
EXTENT OF INJURY. 
It was estimated that the leafhopper caused a loss of $3,000,000 to 
the planters of Hawaii during 1903 and 1904.¢ In the writer’s 
opinion this loss can not be attributed entirely to the leafhopper 
injury. Other species of insects and certain diseases were implicated. 
The leafhopper was directly responsible for the larger percentage of 
loss and indirectly responsible for the unusual development of cer- 
tain diseases. 
In speaking of the rind disease of sugar cane in Hawaii in 1907 
Mr. L. Lewton-Brain says: °: 
To bring before you the actual extent of the loss that the rind disease is now causing 
in your cane fields, I take the following fact obtained by Doctor Cobb from actual 
counts in the field. In one case the cane left on the ground represented about one 
ton of sugar to the acre. That is to say, that if the cane left on the field had been 
sound cane that portion of it left on an acre would produce about a ton of sugar. The 
area counted over, in this particular case, was representative of 200 acres. 
A few years ago, when the leaf-hopper was at the height of its glory in reducing 
the vigour and vitality of your canes, these figures would have been much higher. 
I have been assured that, at that time, there were acres and acres of cane to be seen 
on which the majority of the sticks had been ruined by rind disease. 
Apart from the direct and indirect injury of the leafhopper (Perk- 
imsiella saccharicida Kirk.), the sugar-cane borer (Sphenophorus 
obscurus Boisd.), the sugar-cane leaf-roller (Omiodes accepta Butler), 
and other minor pests contributed to the loss sustained. 
The explanation of, the undue increase on the part of the leaf- 
hopper is made clear when it is known that up to the time of the 
leafhopper invasion the sugar plantations had been particularly free 
from serious attacks of insect and disease pests. The planters were, 
therefore, unacquainted with the insect life to be found in their cane 
fields. They did not know the source or nature of the leafhopper 
attack and had at hand no general knowledge of insect warfare. 
The injury of the leafhopper, combined with that of the other species 
mentioned, and the complications arising through the development 
of certain diseases gave the leafhopper a favorable opportunity to 
develop great numbers in those localities where climatic influences 
or soil conditions were unfavorable to the sugar cane or where a 
deteriorated condition of the cane varieties prevailed. 
2 Report Governor of Hawaii for fiscal year 1907, p. 22. 
6 LewTon-Brain, L.—Rind Disease of the Sugar-Cane. <(Hawaiian Sugar Plant- 
ers, Pxpeista, Dive bath., Bul vei p15. 1907. 
