Mites - Pests of Ornamental Trees, Shrubs and Flowers - page 400

Eriophyes macrochelus (Nalepa) ( 1078-1079 )
Maple leaf gall mite
An often abundant mite on ornamental maple ( Acer )
trees, producing distinctive pouch galls on the leaves.
The galls appear from May onwards, commencing as
greenish warts but later becoming more or less red.
They frequently arise at the junction of the major veins;
they are often very brightly coloured but eventually turn
black. On heavily infested leaves, the galls coalesce and
cause considerable distortion. Mites inhabiting the
galls are c . 0.16 mm long and cylindrical, with about
60 abdominal tergites and sternites, and a relatively
small pair of backwardly directed setae arising from
tubercles on the hind margin of the prodorsal shield.

purplish hairs. Such galls occur from May onwards, and
gradually darken as they mature. Although infested
foliage looks unsightly, tree growth is not affected. The
causal mites are c . 0.18 mm long, with about 65
abdominal tergites and sternites (cf. Aculops acericola ,
p. 406).

AESCULUS

Tegonotus carinatus Nalepa
Horse chestnut rust mite
This widespread and generally common species is free-
living on the underside of the leaves of horse chestnut
( Aesculus hippocastanum ). When present in large
numbers, the mites cause extensive bronzing and
premature leaf fall. Infestations are sometimes of
importance on nursery trees. The mites are c . 0.19 mm
long and rather flattened, with few abdominal tergites;
there are distinct overwintering and summer forms:
deutogynes and protogynes, respectively. The latter are
thought to aestivate within bark crevices on the previous
year's shoots when leaves harden during the early
summer.

Eriophyes psilomerus Nalepa ( 1080 )
The leaves of sycamore ( Acer pseudoplatanus ) are often
disfigured by large, irregular erinea induced by this
generally common gall mite. Each gall appears as a pale
green to brownish blister on the upper surface of the
leaf, with the underside densely clothed in whitish to

1078

ALNUS

Acalitus brevitarsus (Fockeu) ( 1081-1082 )
Alder erineum mite
A generally common pest of various kinds of alder
( Alnus ), infested leaves becoming distorted by large,
irregular, blister-like erinea. The upper surface of each
gall is pale, somewhat warty and shiny; below, the
galled tissue is densely coated with whitish to pale
brown, multi-headed hairs. The galls develop from June
to October, changing in colour from light green, through
pale yellow, to reddish brown. The inhabitants are
c . 0.16 mm long, with about 60 abdominal tergites and

1078 Young galls of maple leaf gall mite ( Eriophyes
macrochelus ).

1079 1080

1079 Maple leaf gall mite ( Eriophyes macrochelus ) damage to
foliage of Acer .

1080 Galls of Eriophyes psilomerus on underside of leaf of
Acer pseudoplatanus .