264 
THE NATIONAL NURSERYMAN 
thing in the way of tree building, both for adornment and 
the protection of their roads, and here in Pennsylvania, 
the state highway engineers have made use of trees as 
windbrakes or snow screens, although in other places 
where natural growth has contributed to the banking of 
snow it has been cut down without substituting an or¬ 
derly line of shading. Save for the park roads and boule¬ 
vards, where generally the tree has been given recog¬ 
nition, and for the natural forest-growth, tree-planting 
is an unfamiliar branch of the science and art of road¬ 
building in America. 
One of the main roads running out of the city of Los 
Angeles is lined on either side, for a distance of more 
than twenty miles, with rose bushes, over eight thousand 
settings being required. The average road-building en¬ 
gineer would call that a luxury—possibly a folly. A few 
years ago an appropriation was made on one of the Eas¬ 
tern railroads for the planting of rambling roses along 
the embankments and cuts beside the right of way on its 
main line for a distance of many miles, and “practical” 
railroad men called it foolishness, although patrons of the 
road found in the beauty of the flowers something to 
take their minds off other incidentals of their journey 
that were more “practical” but nevertheless neglected. 
Beauty and utility often merge. Ordinarily they can be 
made to co-operate. It isn’t necessary that a railroad 
route should be a road-bed and nothipg more, and that 
nature’s deficiency in scenic attraction should be aggra¬ 
vated by eyesores of negligence or design. Nor is there 
good reason why beauty and the eye for it should not be 
served “on the side,” in road-building, at least to the ex¬ 
tent of providing the “setting” of shady green. 
TWO LEAF-HOPPERS INJURIOUS TO APPLE 
NURSERY STOCK 
A. J. Ackerman \U. S. Dept. Agr. Bui. 805 {1919)—This 
is a report of studies of Empoasca mali and Empoa 
rosae conducted at West Chester, Pa., during 
the seasons 1915 and 1916 and supple¬ 
mented by field observations in south¬ 
eastern Pennsylvania and western 
Maryland. 
Investigations made of the more injurious species, E. 
mali. Its attack on nursery apple trees results in the 
leaves becoming undersized and curled which causes a 
decided check to the growth of the new wood. Curling 
begins at the apex and extends toward the base of the 
leaves, the lower surface always being rolled in. The 
leaves become wrinkled, and the loss of sap causes the 
tips to gradually dry up and turn brown. 
In the vicinity of West Chester, Pa., there are three 
broods during the season and three corresponding checks 
in the terminal growth. The first brood is the most abun¬ 
dant on apple and causes more injury than either of the 
two following. As a result of the continued checking of 
the growth, nursery apple trees often require an addi¬ 
tional year’s growth before they become of marketable 
size. Seedlings and the initial growth of buds and grafts 
are very seriously injured, but after the first year’s 
growth the more vigorous varieties become partially im¬ 
mune to injury and succeed in maintaining a satisfactory 
growth, while slow-growing and tender-leaved varieties 
are at all times badly injured by the attack. Among the 
varieties most severely injured in Pennsylvania nurser¬ 
ies are the Red Astrachan, a particularly slow grower 
during the first two seasons, which ranks first, followed 
by Smith Cider, Starr, Early Harvest, Summer Rambo, 
Delaware Winter, Wagoner, Golden Russet, Early Ripe, 
Wealthy, and Alexander. Three other species (Empoasca 
birdii, E. flavescens, and E. unicolor) were found asso¬ 
ciated with E. mali on nursery apple trees at West Ches¬ 
ter. The injury caused by E. unicolor in the vicinity of 
West Chester was negligible. 
In southeastern Pennsylvania E. mali hibernates only 
in the adult stage. The eggs are laid singly in the sides 
of the mid-vein and occasionally in the smaller veins of 
the terminal leaves. The average length of incubation 
of the first brood of eggs is one week. The feeding period 
of the first brood nymphs extends from May 30 to about 
July 15, varying from 15 to 22 days, with an average of 
18.7 days. The second brood eggs hatch from the latter, 
part of June to about August 1, the length of the incuba¬ 
tion period being about one week, and the average length 
of the second nymphal period 15.8 days. The third 
brood eggs hatch from July 30 to about September 1, 
the incubation period being about 9 to 10 days and the 
average length of nymphal period 18.7 days. The win¬ 
ter is passed in the adult stage under rubbish in the nur¬ 
sery or more often under accumulations of leaves in ad¬ 
joining woodlands. 
E. rosae, while primarily a pest of cultivated roses and 
apples, is a rather general feeder. The nymphs and 
adults confine their feeding entirely to the lower leaves 
of apple trees in the nursery. Their injury is caused by 
the sucking of the plant juices as indicated by a mottling 
of the leaves with yellowish or whitish spots at the points 
where the punctures were made. When the leaves be¬ 
come heavily infested they turn yellow, dry up, and drop 
to the ground prematurely. The foliage is never curled 
by this species, nor is the terminal growth checked as in 
the case of injury by E. mali. A second type of injury is 
produced by the egg punctures made by the females in 
the fall during the ovi-position period. The eggs are de¬ 
posited under the bark of young apple trees, several hun¬ 
dred eggs often being placed on a single twig. As com¬ 
pared with the more destructive E. mali, the injury pro¬ 
duced by E. rosae to apple nursery stock is of little im¬ 
portance. 
E. rosae is two-brooded at West Chester, and hiber¬ 
nates in the egg stage, the eggs being deposited singly, 
largely under the bark of apple trees, and rose bushes. 
In the nursery these eggs hatch from May 1 to 15, or 
about a month earlier than those of E. Mali. About one 
month is required for the development of the first brood 
nymphs. The incubation period of the second brood 
eggs is about 25 days, hatching commencing about July 
20. The second brood nymphs require a period of 17 
days lor development. The winter eggs are deposited 
throughout the month of October. Parasites appear to 
play a more important role in reducing the numbers of 
E. rosae A han they do in reducing the more injurious E. 
mali. Larvae ol dryinid parasites are quite common on 
the adults ol E. rosae, but have rarely been found attack¬ 
ing E. mali. Anagrus epos and A. armatus nigriventris, 
parasites ol the winter egg of E. rosae, help considerably 
