SAPINDACEZ. 
SILVA OF NORTH AMERICA. 
Sl 
Acer is attacked by a number of injurious insects,’ and is affected, although not very seriously, by 
various fungal diseases.” 
Acer, the classical name of the Maple-tree, was adopted for the genus by Tournefort,’ and after- 
wards by Linnzeus. 
1 The Maples are liable to serious injury from the attacks of sev- 
eral species of wood-boring insects which are particularly destructive 
to trees planted for shade or ornament, or growing in open sunny 
woods. In America and in Europe the different species are injured 
by many insects. Packard has found thirty-six species (Bull. No. 
7, U. S. Entomolog. Comm. 103), which probably represent but a 
small proportion of those living upon Maple-trees in this country ; 
while Kaltenbach has enumerated no less than sixty-six found on 
these trees in Germany alone (Die Pflanzen-feinde aus der Classe 
der Insecten, 87). The large Sugar Maple borer (Glycobius speci- 
osus) is one of the most dangerous beetles which infest these trees 
in this country, often causing their death (Harris, Insects [njurious 
to Vegetation, ed. 2, 101), and the flat-headed Apple-tree borer 
(Chrysobothris femorata, F.) is sometimes hardly less injurious to 
the Red and Silver Maples (Riley, 1st Ann. Rep. Insects of Missouri, 
1869, 46). 
Clemens) is often very destructive to the Red and Sugar Maples, 
and is especially abundant in some parts of the west. (Riley, 6th 
Ann. Rep. Insects of Missouri, 1874, 107.) The foliage of all the 
species of eastern America is more or less liable to injury by the 
The boring larve of a small moth (geria acerni, 
common Fall Web-worm, and Silver Maples planted in New Eng- 
land cities are sometimes much injured by the larve of the Tussock 
moth. 
The caterpillar of Dryocampa rubicunda, F., sometimes destroys 
the Red and Silver Maples in some parts of the west (Riley, 
5th Ann. Rep. Insects of Missouri, 1873, 137) ; and many other 
leaf-eating and some leaf-mining insects affect the Maples of the 
United States, although their ravages have rarely been serious 
enough to attract general attention. 
Aphids quite frequently infest Maple-trees, and the scale insect 
known as the Cottony Maple Scale (Pulvinaria innumerabilis, Rath- 
von) is often exceedingly troublesome and destructive. (J. D. 
Putnam, Proc. Davenport Acad. ii. 293.) 
Acer Negundo, besides being liable to injury by the boring and 
foliage-eating insects which prey on the other Maples, is peculiarly 
liable to defoliation by the Fall Web-worm (Bull. 10, Div. Ent. 
Dep. Agric. 1887, 40) ; and the Box Elder bug (Leptocoris trivitta- 
tus) is reported as seriously affecting the growth of this tree. (First 
Ann. Rep. Kansas Ex. Station, 1888, 220.) 
2 A considerable number of fungi are parasitic upon Maples. 
As a rule, however, they are comparatively free from serious dis- 
eases caused by fungi, and the species found upon them, while 
possessing much botanical interest, cannot be said to be of great 
importance from the point of view of the arboriculturist. In Eu- 
rope a disease caused by Cercospora acerina, R. Hartig, affects 
seedlings of the different species ; it has not yet been observed, 
however, in this country, where the cultivation of Maples from seed 
is not very often attempted on a large scale. The most striking 
fungal disease of Maples in the United States is that caused by 
Rhytisma acerinum, Fr., which produces black and more or less cir- 
It is 
particularly conspicuous on the narrower lobes of the leaves of the 
cular and thickened spots of considerable size on the leaves. 
Silver Maple, and is also common on the leaves of the Red and 
Sugar Maples. On those species which affect northern or moun- 
tainous regions, such as A. Pennsylvanicum and A. spicatum, a sec- 
ond form (Rhytisma punctatum, Fr.) is more frequently found. It 
differs in appearance from the first species in that the blotches are 
not a uniform black mass, but are aggregations of small black 
spots. The leaves affected with Rhytisma are conspicuous in the 
autumn, although the fungus does not mature until winter and 
after the leaves have fallen. Rhytisma acerinum is common in 
America, where it is found from Maine to Louisiana and California, 
as well as in Europe. Although less conspicuous to the eye, other 
leaf fungi are more injurious to Maples than the Rhytisma. In 
addition to the European species, Gleosporium acerinum, Westd., 
and Phileospora Aceris, Sacc., occur on the Silver Maple in the 
United States, the last being common also on Acer Negundo in 
California. This is the American species first described by Berke- 
ley and Curtis under the name of Spheropsis minima (Grevillea, 
iii. 2), (Phyllosticta acericola, C. & E., Phoma minima, Sacc.), 
which attacks A. barbatum, A. rubrum, and A. Pennsylvanicum in 
the northern states, forming rather small scattered spots which are 
white, thin, and brittle with a black border. This fungus is occa- 
sionally so prevalent as to disfigure and injure the trees. In more 
mountainous districts, A. Pennsylvanicum, especially when young, is 
badly infested by Septoria acerina (25th Ann. Rep. N. Y. State Mu- 
seum, 87), which forms brown irregularly polygonal spots on which 
are sprinkled the brownish fruit dots. When abundant and mature 
this fungus sometimes covers the leaves, and the copious spores 
exude in powdery whitish masses. 
Of fungi belonging to the Perisporiacee or mildews, Uncinula 
circinata, C. & P., replacing the European U. Aceris, is common on 
nearly all the Maples of the northern states. This plant forms a 
thin white mesh with scattered minute black globules usually on 
the under side of the leaves. Of the species of fungi found on the 
trunks and branches of Maples, the greater portion belong to the 
Pyrenomycetes and Hymenomycetes. Most of these species, which are 
found also on other trees, are not known to produce any serious or 
widespread disease on Maples. 
3 Inst. 615, t. 386. 
