Mites - Pests of Ornamental Trees, Shrubs and Flowers - page 408

MALUS on various other kinds of Prunus , including

ornamentals. Affected foliage becomes distinctly
bronzed and may develop a characteristic yellowish
flecking; small blotches sometimes also appear on the
new wood of the young shoots. Damage of greatest
significance is caused in the early spring by the
overwintered mites as they feed on the newly
developing tissue. This species is deuterogenous, with
distinct winter and summer forms. Deutogynes are
c . 0.16 mm long, with about 32 abdominal tergites and
sternites; protogynes are c . 0.17 mm long, with about
30 abdominal tergites and 50 sternites.

Aculus schlechtendali (Nalepa)
Apple rust mite
Although more frequently reported as a pest in apple
orchards, infestations of this generally common species
also occur on crab-apple ( Malus ) and are occasionally
of significance on young trees. The mites are c . 0.17 mm
long and yellowish brown; they are deuterogenous,
breeding throughout the spring and summer on the
underside of leaves. Deutogynes shelter during the
winter in bark crevices and beneath bud scales. Heavy
infestations lead to bronzing and shrivelling of the
foliage, and may also affect the growth of new shoots.

Eriophyes padi (Nalepa) ( 1103 )
Plum leaf gall mite
The erect, dark red leaf galls produced by this locally
common species occur on blackthorn ( Prunus spinosa )
and certain other species of Prunus , and are sometimes
of significance on nursery stock. The galls, which are
very noticeable, tend to occur in tight clusters towards
the middle of the base of the leaf blade. However, they
cause only slight distortion, and do not affect tree
growth. Occupants of the galls are c . 0.22 mm long,
with about 55 abdominal tergites and sternites.

Eriophyes pyri
Pear leaf blister mite
See under Sorbus , p. 419

Phyllocoptes goniothorax malinus
Apple leaf erineum mite
See under Crataegus , p. 411

POPULUS

Aceria dispar (Nalepa)
Associated with aspen ( Populus tremula ), the mites
infesting the young, lateral shoots. Affected leaves are
rolled and crinkled, and the internodes of heavily
infested shoots become noticeably shortened, to form
brush-like clumps of small, deformed leaves.

Eriophyes similis (Nalepa) ( 1104 )
Plum pouch-gall mite
A widespread and locally common pest, often
established in the wild on blackthorn ( Prunus spinosa ).
Infestations also occur on ornamental Prunus , including
nursery trees. The pale greenish to yellowish or reddish,
pouch-like galls tend to occur around the periphery of
the leaves, sometimes resulting in considerable
distortion. The causal mites are c . 0.2 mm long, with
about 50 abdominal tergites and sternites.

Phyllocoptes populi (Nalepa) ( 1101 )
Poplar erineum mite
Associated with aspen ( Populus tremula ) and black
poplar ( P. nigra ), inhabiting erinea on the underside of
the leaves. The upper surface of affected leaves is
disfigured by the development of pallid, blister-like
areas. These galls should not be confused with similar
distortions caused on poplar by the generally common
fungal disease Taphrina populina , which produces
bright yellow blisters on the underside of the leaves; in
the case of the disease the upper surface of an infected
leaf, although noticeably distorted, remains green.

RHODODENDRON

Aculus atlantazaleae (Keifer) ( 1105-1106 )
Azalea bud & rust mite
Although formerly restricted to North America, this pest
is now established in various parts of Europe, including
southern England and the Netherlands. Infestations
occur on certain kinds of azalea ( Rhododendron ),
especially Mollis hybrids. The pale yellowish-brown
mites ( c . 0.17 mm long) feed on the leaf bases and buds,
and cause considerable distortion. They also occur on
the expanding or expanded leaves, and such infestations
result in noticeable bronzing of the foliage.

PRUNUS

Aculus fockeui (Nalepa & Trouessart) ( 1102 )
Plum rust mite
Although mainly a pest in damson and plum orchards,
infestations of this generally common species also occur