17 
ERINOSE. 
SYMPTOM S. 
On February 3, 1916, attention was called to a disease or injury of 
the litchi caused by mites which is here designated as erinose because 
of its similarity in appearance and cause to the erinose of the grape 
and other plants. The tree most affected is the oldest and has been 
one of the most prolific litchis in Hawaii, while within 100 feet of it 
two younger trees were found slightly affected. 
In the early stages of the malady small galls or wartlike swellings, 
often not more than one-sixteenth of an inch in diameter and half 
as high, appear upon the upper surface of the leaf without producing 
any discoloration. On the under surface may be seen brown spots, 
which very early begin to form depressions corresponding to the 
swellings upon the upper surface. The galls increase in size as the 
trouble progresses and may become an inch or more in diameter. 
(See PI. V, fig. 1; PI. IV, fig. 2.) Frequently the affected areas 
become confluent, involving nearly the entire leaflet and giving rise 
to a much crinkled condition of the upper and a brown velvety cov- 
ering on the under surface. Plate V, figure 1, center, shows a leaf 
in which all the leaflets are involved and only a few small areas 
remain green. The velvety covering may extend also to the petiole 
or leaf stock, and in advanced stages it is found even on the young 
twigs. 
A powerful hand lens shows that the velvety covering is composed 
of innumerable trichomes (plant hairs), and the trained eye occa- 
sionally can distinguish the mites which are the cause of the trouble, 
though these will escape the attention of anyone unfamiliar with 
them. With a compound microscope, magnifying about 40 diame- 
ters, the mites are plainly visible in vast numbers among the trichomes. 
Specimens of this mite have been submitted for identification to 
Dr. L. O. Howard, Chief of the Bureau of Entomology, of the Depart- 
ment of Agriculture, who reports that the mite is apparently an 
undescribed species of Eriophyes (PI. V, iig. 2), the genus responsible 
for similar diseases of other plants. 
REMEDIES. 
On February 11, 1916, three different treatments were tried. The 
tree which was most severely attacked was sprayed with a solution 
of 10 ounces nicotin sulphate and 1| pounds whale-oil soap in 50 
gallons of water. This tree, about 48 feet in height and 48 feet in 
spread, received 50 gallons of spray in the attempt to reach every 
part. The second tree, with a height of 20 feet and a spread of 28 
feet, was treated with 4] pounds of resublinied flowers of sulphur 
